The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
A vehicle may be brought into the dealer for a reduced power message, and DTCs P0120, P0220, P1516, P2101, or P2135.
The Throttle Actuator Control (TAC) / throttle body type trouble codes, may be caused by a loose wiring crimp at the throttle body connector, or a broken throttle body circuit.
Recommendation/Instructions:
Complete the current SI diagnostics for any symptoms or trouble codes found. If a intermittent T/P or TAC module type code is occurring complete the inspections below.
Inspect all related throttle body terminals for a loose wiring crimp. The loose crimp may be difficult to find, and the poor connection will be between the terminal and the copper strands of the wire. Wiggle test the individual throttle body circuits to see if the concern can be duplicated.
Inspect the related circuits for broken wires inside the insulation. The outer wire insulation may look fine, but the internal copper strands may be partially broken. Breaks in the wires usually occur within 1 to 4 inches of the throttle body connector. Wiggle testing may also induce a trouble code to set.
On C/K trucks complete SI procedures for voltage drop on grounds G103 and G104. Grounds G103 or G104 may be loose or corroded.
If a terminal crimp or a broken wire has been found, repair or replace only the circuits involved. There is a throttle body pigtail connector available through GMSPO, but installing this pigtail connector may cause other intermittent TAC module/TP codes at a later date. If this pigtail must be used, please follow the SI procedures for Splicing Copper Wire Using Splice Sleeves. (the proper Kent-Moore crimping tool must be used for this repair)
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.
DTC P1516
Circuit Description
The commanded throttle position is compared to the actual throttle position based on accelerator pedal position (APP) and possibly other limiting factors. Both values should be within a calibrated range of each other. The engine control module (ECM) continuously monitors the commanded and actual throttle positions. This DTC sets if the values are greater than the calibrated range.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P1516 Throttle Actuator Control (TAC) Module Throttle Actuator Position Performance
Conditions for Running the DTC
• The ignition is ON.
• The ignition voltage is greater than 6.5 volts.
• The system is not in the battery save mode.
• The engine is running.
• DTCs P0068, P2119, and P2176 are not set.
Conditions for Setting the DTC
The difference between the predicted and the actual throttle position is more than a calibrated amount.
Action Taken When the DTC Sets
The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records.
The control module commands the TAC system to operate in the Reduced Engine Power mode.
A message center or an indicator displays Reduced Engine Power.
Under certain conditions the control module commands the engine OFF.
Conditions for Clearing the MIL/DTC
• The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
• A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
• A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
• Clear the MIL and the DTC with a scan tool.
Diagnostic Aids
The throttle valve are spring loaded to a slightly open position. The throttle valve should be open approximately 20-25 percent. This is referred to as the rest position. The throttle valve should not be completely closed nor should they be open any more than the specified amount. The throttle valve should move open and to the closed position without binding under the normal spring pressure. The throttle should NOT be free to move open or closed WITHOUT spring pressure. Replace the throttle body if any of these conditions are found.
Important: Operating the throttle blade with the Throttle Blade Control function of the scan tool may cause additional DTCs to set. Do not attempt to diagnose DTCs set during this function.
The scan tool has the ability to operate the throttle control system using special functions. Actuate the throttle valve using the throttle blade control function located in the TAC system menu. This function will operate the throttle valve through the entire range in order to determine if the throttle body and system operate correctly.
Check for the following conditions:
• Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
• Poor connections at the ECM or at the component--Inspect the harness connectors for a poor terminal to wire connection. Refer to Testing for Intermittent Conditions and Poor Connections for the proper procedure.
• For intermittents, refer to Testing for Intermittent Conditions and Poor Connections .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
The throttle valve is spring loaded in a slightly open position and should move in either direction without binding. The throttle valve should always be under spring pressure.
When the ignition is turned ON, the ECM operates the throttle control motor to verify the integrity of the system prior to start-up. This can be seen by the momentary flash of the test lamp as the ignition is turned ON.
Step
Action
Values
Yes
No
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Engine Controls Connector End Views or Engine Control Module (ECM) Connector End Views
1
Did you perform the Diagnostic System Check - Vehicle?
--
Go to Step 2
Go to Diagnostic System Check - Vehicle
2
Are DTCs P0120, P0220, P2120, P2125, P2135, P2138 also set?
--
Go to Diagnostic Trouble Code (DTC) List - Vehicle
Go to Step 3
3
Important: The throttle angle and pedal angle may not correspond during this procedure.
Turn ON the ignition, with the engine OFF.
Observe the throttle position (TP) sensor 1 and 2 angle parameters.
Apply and release the accelerator pedal several times.
Does the TP sensor 1 and 2 angle parameters increase as the pedal is applied and decrease as the pedal is released?
--
Go to Step 4
Go to Step 5
4
Observe the Freeze Frame/Failure Records for this DTC.
Start the engine.
Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
Did the DTC fail this ignition?
--
Go to Step 5
Go to Diagnostic Aids
5
Turn ON the ignition, with the engine OFF.
Probe both sides of the ECM 2 fuse with a test lamp connected to ground.
Does the test lamp illuminate on both sides of the fuse?
--
Go to Step 6
Go to Step 16
6
Turn OFF the ignition.
Probe both sides of the ECM 2 fuse with a test lamp connected to ground.
Does the test lamp illuminate on both sides of the fuse?
--
Go to Step 22
Go to Step 7
7
Turn OFF the ignition.
Disconnect the engine control module (ECM) connector containing the ignition 1 voltage circuit from the powertrain relay.
Measure the resistance of the ignition 1 voltage circuit from the ECM electrical connector to the ECM 2 fuse with a DMM. Refer to Troubleshooting with a Digital Multimeter .
Does the resistance measure less than the specified value?
3 ohms
Go to Step 8
Go to Step 23
8
Turn OFF the ignition.
Inspect the throttle body for the following conditions. Refer to Diagnostic Aids:
- A throttle valve that is NOT in the rest position.
- A throttle valve that is binding open or closed.
- A throttle valve that is free to move open or closed WITHOUT spring pressure.
Did you find any of these conditions with the throttle body?
--
Go to Step 24
Go to Step 9
9
Important: The test lamp may momentarily flash when testing these circuits. This is considered normal.
Disconnect the throttle body harness connector.
Turn ON the ignition, with the engine OFF.
Probe the throttle actuator control (TAC) motor control 1 and 2 circuits with the test lamp connected to ground.
Did the test lamp illuminate and remain illuminated on either circuit?
--
Go to Step 13
Go to Step 10
10
Important: The test lamp may momentarily flash when testing these circuits. This is considered normal.
Probe the TAC motor control 1 and 2 circuits with the test lamp connected to battery positive.
Did the test lamp illuminate and remain illuminated on either circuit?
--
Go to Step 14
Go to Step 11
11
Turn OFF the ignition.
Connect the test lamp between the TAC motor control 1 and battery ground.
Important: Ensure that the ECM completely powers down. This can be verified by loss of communication with the scan tool.
Observe the test lamp as you turn ON the ignition.
Does the test lamp flash ON and then turn OFF?
--
Go to Step 12
Go to Step 15
12
Turn OFF the ignition.
Connect a test lamp between the TAC motor control 2 circuit and battery ground.
Important: Ensure that the ECM completely powers down. This can be verified by loss of communication with the scan tool.
Observe the test lamp as you turn ON the ignition.
Does the test lamp flash ON and then OFF?
--
Go to Step 18
Go to Step 15
13
Turn OFF the ignition.
Disconnect the ECM connector that contains the TAC motor control circuits.
Turn ON the ignition, with the engine OFF.
Probe the TAC motor control 1 and 2 circuits with the test lamp connected to ground.
Does the test lamp illuminate?
--
Go to Step 20
Go to Step 19
14
Turn OFF the ignition.
Disconnect the ECM connector that contains the TAC motor control circuits.
Probe the TAC motor control 1 and 2 circuits with the test lamp connected to battery positive.
Does the test lamp illuminate?
--
Go to Step 21
Go to Step 19
15
Turn OFF the ignition.
Disconnect the ECM connector that contains the TAC motor controls circuits.
Test the TAC motor control 1 and 2 circuits for an open or high resistance.
Repair the circuit as necessary. Refer to Wiring Repairs .
Did you find and correct the condition?
--
Go to Step 26
Go to Step 19
16
Test the ignition 1 voltage circuit from the powertrain relay for a short to ground. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?
--
Go to Step 26
Go to Step 17
17
Test the motor control 1 circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?
--
Go to Step 26
Go to Step 24
18
Test for a poor connection or terminal tension at the throttle body connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .
Did you find and correct the condition?
--
Go to Step 26
Go to Step 24
19
Test for a poor connection or terminal tension at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .
Did you find and correct the condition?
--
Go to Step 26
Go to Step 25
20
Repair the short to voltage on the circuit where the test lamp remained illuminated. Refer to Wiring Repairs .
Did you complete the repair?
--
Go to Step 26
--
21
Repair the short to ground on the circuit where the test lamp remained illuminated. Refer to Wiring Repairs .
Did you complete the repair?
--
Go to Step 26
--
22
Repair the short to voltage on the ignition 1 voltage circuit from the powertrain relay. Refer to Wiring Repairs .
Did you complete the repair?
--
Go to Step 26
--
23
Repair the open or high resistance in the ignition 1 voltage circuit from the powertrain relay. Refer to Wiring Repairs .
Did you complete the repair?
--
Go to Step 26
--
24
Replace the throttle body assembly. Refer to Throttle Body Assembly Replacement .
Did you complete the replacement?
--
Go to Step 26
--
25
Replace the ECM. Refer to Control Module References for replacement, setup, and programming.
Did you complete the replacement?
--
Go to Step 26
--
26
Clear the DTCs with a scan tool.
Turn OFF the ignition for 30 seconds.
Start the engine.
Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
Did the DTC fail this ignition?
--
Go to Step 2
Go to Step 27
27
Observe the Capture Info with a scan tool.
Are there any DTCs that have not been diagnosed?
--
Go to Diagnostic Trouble Code (DTC) List - Vehicle
System OK
--------------------------------------------------------------------------------
Document ID# 1615205
2006 Chevrolet TrailBlazer - 4WD
Subject: Information on Normal APP and TP Signal Circuit 2 Voltage Fluctuation - keyword DTC low MIL P0122 P0123 P0220 P0222 P01120 P1220 P1221 P1271 P1275 P1280 P1512 P1514 P1515 P1523 P2101 P2120 P2122 P2123 #PIP3461 - (06/08/2005)
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
If the APP sensor 2 or TP sensor 2 signal circuit is monitored with an oscilloscope or Fluke 87 DVOM on the 1 ms min/max setting, it may be noted that the signal voltage decreases every 156 ms for 6.25 - 7.8 ms each time.
Recommendation/Instructions:
It is normal for these voltages to drop as described above. This is the result of the PCM testing the APP and TP sensors for internal shorts. During the PCM test for a DTC P2135 (P1221 on 02-03 Vue), the PCM shorts the TP sensor 2 signal to ground every 156 ms for 6.25 - 7.8 ms each time. During the PCM test for a DTC P2138 (P1271 on 02-03 Vue), the PCM shorts the APP sensor 2 signal to ground every 156 ms for 6.25 - 7.8 ms each time. At this time, the PCM monitors the APP sensor 1 and TP sensor 1 signal circuit voltages to ensure that they do not decrease with the sensor 2 signal circuits. If they do, an internal sensor short is present or the signal circuits are shorted together.
If there are no DTCs resetting but toggling voltages are encountered during inspection with an oscilloscope or Fluke 87 DVOM on the 1 ms min/max setting, no repairs should be attempted to prevent the voltages from toggling as it is a normal condition. If DTCs are resetting, follow the related SI diagnostic charts to diagnose the ETC system.
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.
DTC P2101
Circuit Description
The commanded throttle position is compared to the actual throttle position based on accelerator pedal position (APP) and possibly other limiting factors. Both values should be within a calibrated range of each other. The engine control module (ECM) continuously monitors the commanded and actual throttle positions. This DTC sets if the values are greater than the calibrated range.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P2101 Control Module Throttle Actuator Position Performance
Conditions for Running the DTC
• The ignition is ON.
• The ignition voltage is more than 6.5 volts.
• The system is not in the battery save mode.
• The engine is running.
• DTCs P0068, P2119, P2176 are not set.
Conditions for Setting the DTC
The difference between the predicted and the actual throttle position is more than a calibrated amount.
Action Taken When the DTC Sets
The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records.
The control module commands the TAC system to operate in the Reduced Engine Power mode.
A message center or an indicator displays Reduced Engine Power.
Under certain conditions the control module commands the engine OFF.
Conditions for Clearing the MIL/DTC
• The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
• A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
• A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
• Clear the MIL and the DTC with a scan tool.
Diagnostic Aids
The throttle valve are spring loaded to a slightly open position. The throttle valve should be open approximately 20-25 percent. This is referred to as the rest position. The throttle valve should not be completely closed nor should they be open any more than the specified amount. The throttle valve should move open and to the closed position without binding under the normal spring pressure. The throttle should NOT be free to move open or closed WITHOUT spring pressure. Replace the throttle body if any of these conditions are found.
Important: Operating the throttle blade with the Throttle Blade Control function of the scan tool may cause additional DTCs to set. Do not attempt to diagnose DTCs set during this function.
The scan tool has the ability to operate the throttle control system using special functions. Actuate the throttle valve using the throttle blade control function located in the throttle actuator control (TAC) system menu. This function will operate the throttle valve through the entire range in order to determine if the throttle body and system operate correctly.
Check for the following conditions:
• Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
• Poor connections at the ECM or at the component--Inspect the harness connectors for a poor terminal to wire connection. Refer to Testing for Intermittent Conditions and Poor Connections for the proper procedure.
• For intermittents, refer to Testing for Intermittent Conditions and Poor Connections .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
The throttle valve is spring loaded in a slightly open position and should move in either direction without binding. The throttle valve should always be under spring pressure.
When the ignition is turned ON, the ECM operates the throttle control motor to verify the integrity of the system prior to start-up. This can be seen by the momentary flash of the test lamp as the ignition is turned ON.
Step
Action
Values
Yes
No
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Engine Control Module (ECM) Connector End Views or Engine Controls Connector End Views
1
Did you perform the Diagnostic System Check - Vehicle?
--
Go to Step 2
Go to Diagnostic System Check - Vehicle
2
Are DTCs P0120, P0220, P2120, P2125, P2135, P2138 also set?
--
Go to Diagnostic Trouble Code (DTC) List - Vehicle
Go to Step 3
3
Important: The throttle angle and pedal angle may not correspond during this procedure.
Turn ON the ignition, with the engine OFF.
Observe the throttle position (TP) sensor 1 and 2 angle parameters.
Apply and release the accelerator pedal several times.
Does the TP sensor 1 and 2 angle parameters increase as the pedal is applied and decrease as the pedal is released?
--
Go to Step 4
Go to Step 5
4
Observe the Freeze Frame/Failure Records for this DTC.
Start the engine.
Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
Did the DTC fail this ignition?
--
Go to Step 5
Go to Diagnostic Aids
5
Turn ON the ignition, with the engine OFF.
Probe both sides of the ECM 2 fuse with a test lamp connected to ground.
Does the test lamp illuminate on both sides of the fuse?
--
Go to Step 6
Go to Step 16
6
Turn OFF the ignition.
Probe both sides of the ECM 2 fuse with a test lamp connected to ground.
Does the test lamp illuminate on both sides of the fuse?
--
Go to Step 22
Go to Step 7
7
Turn OFF the ignition.
Disconnect the engine control module (ECM) connector containing the ignition 1 voltage circuit from the powertrain relay.
Measure the resistance of the ignition 1 voltage circuit from the ECM electrical connector to the ECM 2 fuse with a DMM. Refer to Troubleshooting with a Digital Multimeter .
Does the resistance measure less than the specified value?
3 ohms
Go to Step 8
Go to Step 23
8
Turn OFF the ignition.
Inspect the throttle body for the following conditions. Refer to Diagnostic Aids:
- A throttle valve that is NOT in the rest position.
- A throttle valve that is binding open or closed.
- A throttle valve that is free to move open or closed WITHOUT spring pressure.
Did you find any of these conditions with the throttle body?
--
Go to Step 24
Go to Step 9
9
Important: The test lamp may momentarily flash when testing these circuits. This is considered normal.
Disconnect the throttle body harness connector.
Turn ON the ignition, with the engine OFF.
Probe the throttle actuator control (TAC) motor control 1 and 2 circuits with the test lamp connected to ground.
Did the test lamp illuminate and remain illuminated on either circuit?
--
Go to Step 13
Go to Step 10
10
Important: The test lamp may momentarily flash when testing these circuits. This is considered normal.
Probe the TAC motor control 1 and 2 circuits with the test lamp connected to battery positive.
Did the test lamp illuminate and remain illuminated on either circuit?
--
Go to Step 14
Go to Step 11
11
Turn OFF the ignition.
Connect the test lamp between the TAC motor control 1 and battery ground.
Important: Ensure that the ECM completely powers down. This can be verified by loss of communication with the scan tool.
Observe the test lamp as you turn ON the ignition.
Does the test lamp flash ON and then turn OFF?
--
Go to Step 12
Go to Step 15
12
Turn OFF the ignition.
Connect a test lamp between the TAC motor control 2 circuit and battery ground.
Important: Ensure that the ECM completely powers down. This can be verified by loss of communication with the scan tool.
Observe the test lamp as you turn ON the ignition.
Does the test lamp flash ON and then OFF?
--
Go to Step 18
Go to Step 15
13
Turn OFF the ignition.
Disconnect the ECM connector that contains the TAC motor control circuits.
Turn ON the ignition, with the engine OFF.
Probe the TAC motor control 1 and 2 circuits with the test lamp connected to ground.
Does the test lamp illuminate?
--
Go to Step 20
Go to Step 19
14
Turn OFF the ignition.
Disconnect the ECM connector that contains the TAC motor control circuits.
Probe the TAC motor control 1 and 2 circuits with the test lamp connected to battery positive.
Does the test lamp illuminate?
--
Go to Step 21
Go to Step 19
15
Turn OFF the ignition.
Disconnect the ECM connector that contains the TAC motor controls circuits.
Test the TAC motor control 1 and 2 circuits for an open or high resistance.
Repair the circuit as necessary. Refer to Wiring Repairs .
Did you find and correct the condition?
--
Go to Step 26
Go to Step 19
16
Test the ignition 1 voltage circuit from the powertrain relay for a short to ground. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?
--
Go to Step 26
Go to Step 17
17
Test the motor control 1 circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?
--
Go to Step 26
Go to Step 24
18
Test for a poor connection or terminal tension at the throttle body connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .
Did you find and correct the condition?
--
Go to Step 26
Go to Step 24
19
Test for a poor connection or terminal tension at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .
Did you find and correct the condition?
--
Go to Step 26
Go to Step 25
20
Repair the short to voltage on the circuit where the test lamp remained illuminated. Refer to Wiring Repairs .
Did you complete the repair?
--
Go to Step 26
--
21
Repair the short to ground on the circuit where the test lamp remained illuminated. Refer to Wiring Repairs .
Did you complete the repair?
--
Go to Step 26
--
22
Repair the short to voltage on the ignition 1 voltage circuit from the powertrain relay. Refer to Wiring Repairs .
Did you complete the repair?
--
Go to Step 26
--
23
Repair the open or high resistance in the ignition 1 voltage circuit from the powertrain relay. Refer to Wiring Repairs .
Did you complete the repair?
--
Go to Step 26
--
24
Replace the throttle body assembly. Refer to Throttle Body Assembly Replacement .
Did you complete the replacement?
--
Go to Step 26
--
25
Replace the ECM. Refer to Control Module References for replacement, setup, and programming.
Did you complete the replacement?
--
Go to Step 26
--
26
Clear the DTCs with a scan tool.
Turn OFF the ignition for 30 seconds.
Start the engine.
Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
Did the DTC fail this ignition?
--
Go to Step 2
Go to Step 27
27
Observe the Capture Info with a scan tool.
Are there any DTCs that have not been diagnosed?
--
Go to Diagnostic Trouble Code (DTC) List - Vehicle
System OK
__________________ http://www.leftcoast32.com
'07 Black TrailBlazer SS "MP122HH" MagnaCharger
'05 SSR 6 Speed 427 "MP122HH" MagnaCharger Authorized MagnaCharger Dealer/Distributor
Thanks Joe. Good infomation. I would probably want to give this trouble shoot proceedure to the same technicians who it was noted in a thread from yesterday, rotated someones wheels front to rear. It would definately be worth the drive.
With the TSB above you will have stored DTC's which will trigger the Check Engine Light. You should not clear the CEL and go to the dealer so he can read the codes and diagnose the problem from this TSB.
__________________ http://www.leftcoast32.com
'07 Black TrailBlazer SS "MP122HH" MagnaCharger
'05 SSR 6 Speed 427 "MP122HH" MagnaCharger Authorized MagnaCharger Dealer/Distributor
So there is nothing to worry about until the Check Engine Light comes on? Or one can still have the problem with out the warning light light coming on?
And if I take it to the dealer to fix will it affect my HP computer tune?
You guys may be jumping on Ricochet underservedly this time.
I read his comment to be saying "Gosh that's a long list of affected vehciles listed in the TSB. Do they use this same assembly on all or many of the GM vehciles?"
In fact, they likely do use many of the parts that are "standard" as opposed to unique on all or most vehicles. In addition, they appear to be saying the problem could be in thw wire crimping method used. This COULD potentially have very broad impact.
It would definately be worth the drive.
