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Thread: Gen 4 TPS sanity check

  1. #1
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    Gen 4 TPS sanity check

    I think I have a toasted ECM here, possibly wiring but doubtful. It's an E67/T42 from an 08 Trailblazer on a 5.3 swapped into another car. 08 TB factory pedal, but 08 LS4 intake/TB, small cam, headers, intake, nothing special. It seems to work fine, but twice now it's dropped the p0606 and P1516 codes on me and promptly shuts down the engine dead. Both times from light throttle low-speed. I can immediately clear codes and the engine fires up, but if I don't clear them it will not start. I have not changed any ETC settings.

    In the scanner I'm seeing the TPS fluctuate between two numbers constantly on the chart, as you can see in the graph in my attached log. When you replay the log it doesn't show this action, however. When scanning the car live it shows in real time what the graph shows - a TPS that fluctuates like 5 times a second, literally, by 10-30%.

    A brand new LS3 TB does the same thing, and in fact it does it with the TB unplugged, too. Is this some weird scanner behavior or am I seeing a real problem? I have downloaded others' logs and none of them show this behavior.

    The log I've posted is about a 20 minute drive to show this weird TPS in the scanner but doesn't capture the time when the code pops.
    Attached Files Attached Files

  2. #2
    Senior Tuner blindsquirrel's Avatar
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    What harness? Reworked stock or aftermarket?

    One thing I notice is, 'P0606' looks very similar to 'P060D', and as it happens both are on the same page in the service manual. P060D is 'Control Module Accelerator Pedal Position (APP) System Performance'. I have seen diagnostic software misname a DTC - P0116 reported as being P0115, for example. There is no such code as P0115.

    What do you know about the history of the ECM? Have you ever flashed it yourself, if so using what tools, and what did you do? Did it come from a real known-running '08 Trailblazer? Any chance it's been monkeyed with, like had the OS changed using something other than a Tech2/MDI+SPS?

    If you have any doubts about the above, I'd try flashing it with a stock calibration using real proper tools (not HP Tuners). If nothing changes it's time to try a different ECM (as long as it's from the same year/platform you can just plug it in and run the scan without licensing anything, see if the TPS behavior is notably different).

  3. #3
    Senior Tuner blindsquirrel's Avatar
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    According to the Details tab in the log you have the right calIDs for the two hidden segments with the right CVNs, so they're not leftovers and they haven't been monkeyed with. I'd try reflashing it before writing it off.

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    Quote Originally Posted by blindsquirrel View Post
    What harness? Reworked stock or aftermarket?

    One thing I notice is, 'P0606' looks very similar to 'P060D', and as it happens both are on the same page in the service manual. P060D is 'Control Module Accelerator Pedal Position (APP) System Performance'. I have seen diagnostic software misname a DTC - P0116 reported as being P0115, for example. There is no such code as P0115.

    What do you know about the history of the ECM? Have you ever flashed it yourself, if so using what tools, and what did you do? Did it come from a real known-running '08 Trailblazer? Any chance it's been monkeyed with, like had the OS changed using something other than a Tech2/MDI+SPS?

    If you have any doubts about the above, I'd try flashing it with a stock calibration using real proper tools (not HP Tuners). If nothing changes it's time to try a different ECM (as long as it's from the same year/platform you can just plug it in and run the scan without licensing anything, see if the TPS behavior is notably different).
    All your troubleshooting are appreciated, but I'm asking about the fluctuating TPS in the scanner being real or bogus since it doesn't fluctuate at all when replayed. I should have been more to-the-point.

    I pulled the ECM from a Trailblazer in the yard myself and the VIN matches, but it was crashed and of unknown history.

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    Quote Originally Posted by blindsquirrel View Post
    According to the Details tab in the log you have the right calIDs for the two hidden segments with the right CVNs, so they're not leftovers and they haven't been monkeyed with. I'd try reflashing it before writing it off.
    Ever since the first day I turned the key on the TPS has shown this weird oscillation. That's before I even downloaded and licensed it.

  6. #6
    Senior Tuner blindsquirrel's Avatar
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    A scanner playback issue won't cause codes to set or the shutdown after the P1516 sets. It's showing the P0606 as current in that log even before the problem occurs.

    The only way I know to really test for the TPS fluctuation is to substitute a known-good E67.

  7. #7
    Senior Tuner blindsquirrel's Avatar
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    Or, you could put a scope on the TPS1/TPS2 wires with the TB unplugged, see if actual matches reported. I guess it's possible there's noise on the lines from somewhere.

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    Advanced Tuner Shrek's Avatar
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    Quote Originally Posted by realsquash View Post
    ... an E67/T42 from an 08 Trailblazer on a 5.3 swapped into another car. 08 TB factory pedal, but 08 LS4 intake/TB, small cam, headers, intake, nothing special. It seems to work fine, but twice now it's dropped the p0606 and P1516 codes ...
    The 2008 LS4 throttle body is not compatible with the 2008 TBSS electronic throttle control system.

    A P0606 is often set when you have a mismatch of components, with a Gen 4 LS electronic throttle control system.


    Quote Originally Posted by realsquash View Post
    ... A brand new LS3 TB does the same thing ...
    Likewise, an LS3 throttle body is not compatible with the 2008 TBSS electronic throttle control system.

    If you are using a 2008 TBSS E67 ECM and programming, and a 2008 TBSS APP (accelerator pedal), then you need to use a Gen 4 Truck throttle body.

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    Quote Originally Posted by blindsquirrel View Post
    A scanner playback issue won't cause codes to set or the shutdown after the P1516 sets. It's showing the P0606 as current in that log even before the problem occurs.

    The only way I know to really test for the TPS fluctuation is to substitute a known-good E67.
    I'm going to try this and see what happens. I know a playback issue doesn't cause codes. I see a rapid oscillation in the scanner, but the replay of the log doesn't show it.

    Quote Originally Posted by blindsquirrel View Post
    Or, you could put a scope on the TPS1/TPS2 wires with the TB unplugged, see if actual matches reported. I guess it's possible there's noise on the lines from somewhere.
    I might do this once it cools down a little tonight.

    Quote Originally Posted by Shrek View Post
    The 2008 LS4 throttle body is not compatible with the 2008 TBSS electronic throttle control system.

    A P0606 is often set when you have a mismatch of components, with a Gen 4 LS electronic throttle control system.

    Likewise, an LS3 throttle body is not compatible with the 2008 TBSS electronic throttle control system.

    If you are using a 2008 TBSS E67 ECM and programming, and a 2008 TBSS APP (accelerator pedal), then you need to use a Gen 4 Truck throttle body.
    Not sure I agree with the incompatibility in this case, but I'm not here to argue that.

  10. #10
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    Quote Originally Posted by realsquash View Post
    ... Not sure I agree with the incompatibility in this case, but I'm not here to argue that ...

    GM does not care if you agree, or disagree, with their throttle control strategy - it simply is.

    Once you have completed more than one Gen 4 LS conversion, you may come to realize how things actually function.

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    Quote Originally Posted by Shrek View Post
    GM does not care if you agree, or disagree, with their throttle control strategy - it simply is.

    Once you have completed more than one Gen 4 LS conversion, you may come to realize how things actually function.
    Since you have decided to waste your time replying to a peon like me what do you think about the conflicting data in the scanner?

  12. #12
    Senior Tuner blindsquirrel's Avatar
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    Unplug the TB, clear codes - does the P0606 still set with the TB unplugged?

  13. #13
    Senior Tuner blindsquirrel's Avatar
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    So, what is the difference in TP1/TP2 strategy between a 6-pin truck and 6-pin LS4 throttle body? Or is that proprietary knowledge we aren't allowed to know?

  14. #14
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    Quote Originally Posted by blindsquirrel View Post
    So, what is the difference in TP1/TP2 strategy between a 6-pin truck and 6-pin LS4 throttle body? Or is that proprietary knowledge we aren't allowed to know?

    You would have to ask GM why they opted to use multiple throttle body types (often different voltage sweeps or direction of rotation). Likewise from the APP (accelerator pedal) - there are multiple variations - Corvette, Camaro, CTS-V, STS-V, Impala, Trailblazer, and full size Truck - all with unique voltage sweep patterns.

    I try to point people in the right direction to get their projects moving forward. This is something that I do as a kindness, not as some demented exercise in wasting my time arguing with the indignant.

    You gentlemen are on your own from this point forward - good luck.

  15. #15
    Senior Tuner blindsquirrel's Avatar
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    Summary: you don't know.

    According to the manual the description for both is the same (above 4v to less than 1v, less than 1v to more than 4v), but I know that's not the whole story of what it looks for with the TP correlation stuff. I would like to know what is different, not because I think I know the answer and looking to score a 'GOTCHA!', but because I want to know what is different. You have a real problem with reading into things that just are not there.

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    Here's a follow-up: I SPS flashed another E67 (same service number), copied tune changes over and have been driving the wee out of it. No codes, nothing. Throttle body works perfectly all the time. The pedal has to be a Trailblazer for sure, but for the throttle bodies the 6-pin stuff is pretty flexible and this setup works fine. This isn't my first rodeo and I've been kicked a few times.

    And the TPS still flutters in the scanner for some reason, just as it did on the previous ECM. I would still like to know why the real time plot doesn't match the log file. I can't find a setting anywhere that would do any kind of smoothing or other process to change the data and I wonder what else this happens with. I didn't put a scope on it, but if there was really that much noise nothing would run right.

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    Random, but how many tps channels are you logging? If I log 2 by mistake I get the flutter. Then I log 1 and it's smooth as. Just something else to check...

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    Quote Originally Posted by hjtrbo View Post
    Random, but how many tps channels are you logging? If I log 2 by mistake I get the flutter. Then I log 1 and it's smooth as. Just something else to check...
    More than one for sure, I will try that!

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    Quote Originally Posted by hjtrbo View Post
    Random, but how many tps channels are you logging? If I log 2 by mistake I get the flutter. Then I log 1 and it's smooth as. Just something else to check...
    FYI I was logging like all the TPS channels and once I got them pared down to 1 the fluttering went away completely. Thanks a bunch for the suggestion, it was starting to get to me.

  20. #20
    Senior Tuner blindsquirrel's Avatar
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    I suspect that the '07-down 8-pin LS4 throttle body would work too as it has the same TP1/TP2 strategy, it just has redundant 5v/loref pins whereas the 6-pin uses a single 5v/loref for both sensors.