Diagnostics I did over this weekend to address a technical problem uncovered something that might be useful for other Fanatics to know: the accelerator pedal assembly on the 03/04 SSRs is NOT the same as the one on the 05/06 SSRs! And, there are consequences.
Some of you know that at the urging of 2005SSR6speed, I recently installed a 90mm throttle body off his 05 SSR onto my highly modified 04 SSR (which comes stock with a 75 mm thottle body that is also much dirtier aerdynamically). It has been working GREAT at most throttle openings short of WOT, but when I put my foot to the floor, the computer delcares an "engine protection emergency" and forces the engine to idle. This is inconvenient.
Me, 2005SSR6speed, Lyndon Wester (tuner), JohnSpear (Speartech Inc), and others have been trying to figure out what is going on, as the combination of parts I am using works well on numerous Chevy pickups with LM4 engines and electronics. Something in the SSR is different (here we go again). This weekend, I did some diagnostics trying to determine if the acclerator pedal had anything to do with it. Turns out, I did not find anything that solves the problem, bu DID find that the 03/04 and 05/06 pedal assemblies are electronically different. Let me explain that, and how it can affect other Fanatics in either a helpful or adverse way.
First, some background. I had started out of course with a sotck 04 pedal assembly. But, I wanted the accessory ALLOY pedal faces, so I went to GMPartsDirect.com and looked for them. They did not show the alloy pedal face kit for my 04 SSR, but did show a kit for an 05 SSR. I figured that since the pedals are physically identical in appearance and size, the 05 pedal faces would work on my 04 pedals. I ordered the kit. When it arrived, I confirmed that the pedal faces in the kit looked identical to my 04 faces (other than the alloy versus rubber of course). However, I noted that the kit includes an alloy FACE for the brake kit, an alloy dead pedal face, but a complete acclerator pedal assembly. I assumed that this was because the accelerator pedal is PINNED into the accelerator pedal asssembly, and GM doesn't want buyers hacking up a safety-related assembly to switch from rubber to alloy pedal face. I figured no problem, I'll just make the swap and everything will be fine.
I made the swap, and it DID indeed seem fine.
I did notice around that same timethat the throttle response seemed better, but I did not put 2 and 2 together at the time.
Fast forward a couple of weeks to when Randy and I installed the 90mm throttle body. Withut repeating all the details here that are already in my posting on the 90mm throttle body (search using "90 mm throttle body"), we ran into a snag that focused my attention: the inability to apply WOT. We have been working on that for a couple of weeks.
In the meantime, I have been educating myself on a topic I never thought I would want any expertise on: the electronics of electronic throttle control assemblies. Tis is where I got a glimmer that those two acclerator pedal assembliesmight NOT in fact be electronically the same.
My problem was that I could see no good reason for there being more than one "standard" pedal assembly. After all, with the electronic throttle control (ETC) on the SSR, the "response" caused by any movement of the pedal can be programmatically "tuned" in the onboard computer's software to be virtually any response curve you want (subject to some common sense restrictions, like 10% throttle pedal movement will not be accepted as commanding WOT, for safety reasons). So, since customization costs money in design, parts stocking, and programming, I couldn't imagine why Delphi would "wire" the pedal on an 03/04 SSR differently than they would wire an 05/06 SSR pedal, or for that matter, a Corvette pedal. But, I was wrong. I discovered that this weekend.
I took the bellows off my throttle body, placed a flashlight and mirror in front of it so I could see the throttle blade movement clearly from the driver's seat, turned the ignition key (but not engine!) "on", and started playing with the pedal.
Very educational.
It turns out that fairly small initial movement of the 05 pedal causes a pretty substantial reaction at the throttle blade. I kept pushing the pedal further and further, noting the resulting position of the throttle blade. I finally hit a point where the throttle blade was 100% open. Interestingly, the pedal was NOT all the way to its stop. I continued pushing the pedal further in small increments. There was no corresponding blade movement (remember, it was already 100% open). But then, at a certain point of additional pedal movement, the throttle blade abruptly snapped shut!!
I interpreted that to mean that the PCM was now receiving a voltage that was somehow "out of range" for use with the new thottle body. (Remember, this pedal had worked fine with the stock throttle body).
I then went through the hassle of swapping back to the stock 04 pedal assembly, and repeated the testing. With the 04 pedal assembly installed, the throttle blade movement was SMALLER initially (less movement of throttle blade per millimeter of pedal travel), but the blade ended up at 100% open by about the same TOTAL (cumulative) pedal movement. After that, the blade reacted the same way as it had to the 05 pedal when I applied yet more pedal movement: no apaprent response at first, and then at a certain point, the blade snapped shut.
Ok, what have we learned? Well, here is what I see:
- The 05 SSR pedal is more "front end loaded". In other words, when you start applying pedal movement, it generates more blade movement per millimeter of pedal movement than the 04 pedal does.
- However, both pedals hit "100%" blade opening after about the same cumulative amount of pedal movement
- Both pedals cause the "engine protection mode" (blade snaps shut) after a certain amount of "excess" pedal movement
- Both pedals worked just fine with the 75mm throttle body, so the difference is in whatever else has changed, which includes:
- the new 90 mm throttle body
- the new wiring harness adaptor that enables you to plug the new 90mm throttle body into an 03/04 vehicle wiring harness
- The new TAC module (Throttle Acutation Control module) that is required to be instaleld on an 03/04 SSR when using the 05/06 throttle body, because the electornics on the 03/04 are different than those on the 05/06
There is an obvious predictable result for anyone who puts the GM 05/06 pedal face kit onto an 03/04: since the kit includes the 05 pedal assembly, the vehicle will feel friskier at lower throttle settings. Now, you could get that same friskiness, or MORE friskiness, just by having a tuner tune the software in the computer, but this is a pretty easy alternate way to change the throttle feel.
But there is a more important outcome to note: the 03/04 throttle pedal assemblie are not ELECTRONICALLY the same as the 05/06 throttle pedal assemblies, even though they are PHYSICALLY similar in appearance.
The same caution may apply to other assemblies that we might have assumed tobe identical . . .
Jim G
Linear Mode
