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Premium Member
2003 Chevy SSR
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1,562 Posts
Discussion Starter · #1 ·
I have had a very intermittent problem over the past couple months with Ilsa suddenly either going into limp mode then stopping, or (yesterday) just stopping. The engine sputters and coughs a bit then just gives up. It happened once at full throttle at the end of an autocross run. The second time was also during an autocross, but only at about half throttle and only halfway through the fourth run. Yesterday, I was just on a city street around 30mph when she went into it. Amazingly, after a few minutes of rest, she runs fine again!

I thought it sounded like a fuel delivery problem (custom two-pump module with Hobbs switch that activates that second pump at 4 pounds of boost) and was working with the manufacturer on troubleshooting.

In a stroke of luck, I met with a mech friend yesterday afternoon (about putting cutouts on) and mentioned it to him. He pulled out his HP tuner/diagnostic and it showed a problem with the tachometer module (which is on the firewall low on the starboard side).

Before I replace that, may I have advice and comments on this situation?

FYI, she's an early '03 with rebuilt engine, 2.3 l supercharger, headers, and upgraded radiator.
 

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Super Road Rocket Pilot
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6,941 Posts
What code or issue description did you get? I have never heard of a "tachometer module" and the manual does not show anything similar. Could it be called something else?
 

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Premium Member
04 SSR
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4,393 Posts
@Achias and @Dragon2U It's most likely TAC module, not Tach module. This is 03 and 04 models only.
TAC is for throttle actuator control module. I helped another fanatic years ago with this code. There was a TSB regarding this code. I am not where I can look it up.
But may find time later.
Maybe someone can find it if they use proper terminology.

The TAC module is a stand alone module to operate electronic throttle. It communicates to the PCM on a LAN circuit (Local Area Network). In brief, this means it's not on the class 2 network.
This function is done in the ECM on 05 and 06 models.

Check out the TSB, if no luck follow the code diagnostic chart.
 

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Premium Member
04 SSR
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4,393 Posts
That's a LOT of stuff that's WAY over my head. Where should I start?

Dave
I forgot the TSB was that detailed and involved more codes which we don't know if they where present.

So Start by do a good visual inspection of wiring harness near throttle body. I am not sure if they had to modify/lengthen that harness to install super charger, if yes, those connections would be suspect.
Check fuse #20 (ETC) underhood fuse block - its not blown but check clean and tight connections
Check ground G101 - clean and tight

Then ask tech what ALL code numbers were. I need numbers not descriptions.
Report back with ALL code numbers and I can look at diagnostic chart.

The abbreviated version for P1516 TAC contoller.

If system voltage is good -- check for Codes U1007 or P2135
If good ground and voltage to TAC module and codes are not present -- problem is wiring, throttle body unit or tach module.

Testing the circuit to find exact cause is going to be difficult because it is an intermittent condition.

Both the throttle body and the TAC module are plug and play (no programing required)

TAC module part #12588922 - fits other GM models, I don't know which ones - if looking for a used one
Throttle body part # 12570800 - again I don't know if others will work and what they could come from

Used these can found for about $50 - $100 each -- for other models, but I didn't see any listed for SSR so I don't know?

If you consider replacing the TAC module I would al least test power and ground their with a 12 volt test light
One lead to the power wire Pink wire cavity 7 (should be only pink wire) the other to the ground wire Black wire cavity 15 (note 2 black wires) -- key on test light should be nice and bright.

Rectangle Font Slope Parallel Pattern

Line Font Rectangle Parallel Pattern
 

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Premium Member
2003 Chevy SSR
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1,562 Posts
Discussion Starter · #7 ·
It looks like I'm going to have to check the fuel pressure when this is happening. May I have the dunce's guide to attaching a fuel pressure meter under the hood? Is there one that I can leave attached?
 

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SSR Believer
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3,623 Posts
It looks like I'm going to have to check the fuel pressure when this is happening. May I have the dunce's guide to attaching a fuel pressure meter under the hood? Is there one that I can leave attached?
When I suspected a failing fuel pump on our '05 I picked up a "loaner" fuel pressure gauge from O'Reily's. (Free for 48 hours). It attaches to the Schrader valve (basically the same as a tire's valve stem) on the fuel rail. I do not know exactly where yours might attach. I made a video of the test here:

Here's a 5.3L fuel pressure test on a Silverado which may be the same as yours.


Not sure about leaving a pressure gauge attached under the hood, but they do make gauges that mount in the cab.

Hope that helps!
 
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