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TCM/Accelerator Pedal adaptation

Help, Advice, Owners' Discussion and DIY Tutorials on Volvo's stylish, distinctive "P2" platform cars.

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Ftknox1301
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TCM/Accelerator Pedal adaptation

Post by Ftknox1301 » Tue Jan 14, 2020 5:59 pm

Hello everyone, in a previous post I was having issues with my wife's O2 XC70 being stuck in a limp mode after replacing a broken serpentine belt. I'm wondering if while she was driving the car off of the battery power the low voltage may have caused the accelerator pedal to stop communicating with the ECM or something of that nature? After further research I believe that either the throttle control module or the accelerator pedal need to be readapted to the ECM. Does anyone have experience with this process? I was planning on ordering the Vida/Dice software and trying this process. Thanks in advance for any advice.

Codes p2126 and p2121

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Re: TCM/Accelerator Pedal adaptation

Post by highmiles » Wed Jan 15, 2020 10:38 am

I read through your previous post. What is the current state of the car? Is it running at all? Cranks but won't fire? Check engine light?
Does the battery have a full charge?
Have you tried disconnecting the battery all together? It seems I have also heard to wait "x" minutes and or touch the cables together to fully discharge any latent charge in the car.
I have found VIDA to be pretty indispensable in trouble shooting these cars, the generic codes are just not very helpful.

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Re: TCM/Accelerator Pedal adaptation

Post by xHeart » Wed Jan 15, 2020 11:20 am

Ftknox1301 wrote: ↑
Tue Jan 14, 2020 5:59 pm
Hello everyone, in a previous post I was having issues with my wife's O2 XC70 being stuck in a limp mode after replacing a broken serpentine belt. I'm wondering if while she was driving the car off of the battery power the low voltage may have caused the accelerator pedal to stop communicating with the ECM or something of that nature? After further research I believe that either the throttle control module or the accelerator pedal need to be readapted to the ECM. Does anyone have experience with this process? I was planning on ordering the Vida/Dice software and trying this process. Thanks in advance for any advice.

Codes p2126 and p2121
You'll need a fully charged battery set up to come out of LIMP cycle -- it is a fuel shut-off, i.e., ECM taking away AP function from you for safety. VIDA DiCE is must have in your situation.

ETM needs to power down fully to erase its memory before the car is normally driven, otherwise the fault may be set in the ECM again.

For the ECM and ETM to power down fully the ignition should be turned off for 5 minutes each time, if the cooling fan is running you will need to wait until 2 minutes after the cooling fan has stopped to ensure the ETM is powered down.
--
Golden Retriever | 2014D VIDA DiCE | 2013A XC90 +144mi/231km | 2001 V70XC 1st Owner +196mi/ +315km | 1997 Volvo 850 NA 1st Owner +180mi/ +289km
Past: German Shepherd | 1989 Volvo 740 GL | 1979 Volvo 240

Ftknox1301
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Re: TCM/Accelerator Pedal adaptation

Post by Ftknox1301 » Wed Jan 15, 2020 5:03 pm

xHeart wrote: ↑
Wed Jan 15, 2020 11:20 am
Ftknox1301 wrote: ↑
Tue Jan 14, 2020 5:59 pm
Hello everyone, in a previous post I was having issues with my wife's O2 XC70 being stuck in a limp mode after replacing a broken serpentine belt. I'm wondering if while she was driving the car off of the battery power the low voltage may have caused the accelerator pedal to stop communicating with the ECM or something of that nature? After further research I believe that either the throttle control module or the accelerator pedal need to be readapted to the ECM. Does anyone have experience with this process? I was planning on ordering the Vida/Dice software and trying this process. Thanks in advance for any advice.

Codes p2126 and p2121
You'll need a fully charged battery set up to come out of LIMP cycle -- it is a fuel shut-off, i.e., ECM taking away AP function from you for safety. VIDA DiCE is must have in your situation.

ETM needs to power down fully to erase its memory before the car is normally driven, otherwise the fault may be set in the ECM again.

For the ECM and ETM to power down fully the ignition should be turned off for 5 minutes each time, if the cooling fan is running you will need to wait until 2 minutes after the cooling fan has stopped to ensure the ETM is powered down.
Yes I'm definitely going to get the software since I have two of these cars, but should I be able to get the car back to its normal running condition by simply charging up the battery? I have had to jump start the car a few times but I've never put it on the battery charger. I've also had the battery totally disconnected for a few days and also touched the positive and negative battery cables together for a few seconds to clear any codes still in the ECM.

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xHeart

Re: TCM/Accelerator Pedal adaptation

Post by xHeart » Thu Jan 16, 2020 10:32 am

A weak battery prevents ECM from resetting if there is an error code. My experience, a fully charged battery is needed for VIDA/DiCE to communicate without missing signals, hence calling stored instruction "cut off fuel". ETM and AP communication is interrupted due to error code NOT being ERASED -- failed power down procedure.

You can try attaching trickle charger to the battery, and let it charge overnight. AND then try the power down procedure. But it will be a guess work without VIDA/DiCE.

A normal drive cycle is recommended after the RESET for ETM and AP to relearn.
--
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Past: German Shepherd | 1989 Volvo 740 GL | 1979 Volvo 240

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Re: TCM/Accelerator Pedal adaptation

Post by Ftknox1301 » Thu Jan 16, 2020 3:43 pm

xHeart wrote: ↑
Thu Jan 16, 2020 10:32 am
A weak battery prevents ECM from resetting if there is an error code. My experience, a fully charged battery is needed for VIDA/DiCE to communicate without missing signals, hence calling stored instruction "cut off fuel". ETM and AP communication is interrupted due to error code NOT being ERASED -- failed power down procedure.

You can try attaching trickle charger to the battery, and let it charge overnight. AND then try the power down procedure. But it will be a guess work without VIDA/DiCE.

A normal drive cycle is recommended after the RESET for ETM and AP to relearn.
thank you very much for the feedback I do currently have the battery on a trickle charger and we'll take it off tomorrow to see what type of results I get. I will most likely be ordering the software sometime next week and at that point hopefully we'll be able to remedy this issue.

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Re: TCM/Accelerator Pedal adaptation

Post by jimmy57 » Thu Jan 16, 2020 4:06 pm

2002 XC70 does not have Magnetti Marelli ETM, it uses the Bosch electric throttle. The adaptation for that unit can be commanded with VIDA or you turn ignition on without starting engine and wait for about 50 seconds and you'll hear the throttle get cycled twice by ECM to learn the fully open and fully closed TPS signal values.
2002 bosch turbo 5 cyl and 6 cyl engines got the bosch units except for the C70 models which were delayed till 2003. The Denso 5 cylinder non turbo engines switched to Denso electric throttles for 2003.

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Re: TCM/Accelerator Pedal adaptation

Post by Ftknox1301 » Sat Jan 18, 2020 6:31 pm

jimmy57 wrote: ↑
Thu Jan 16, 2020 4:06 pm
2002 XC70 does not have Magnetti Marelli ETM, it uses the Bosch electric throttle. The adaptation for that unit can be commanded with VIDA or you turn ignition on without starting engine and wait for about 50 seconds and you'll hear the throttle get cycled twice by ECM to learn the fully open and fully closed TPS signal values.
2002 bosch turbo 5 cyl and 6 cyl engines got the bosch units except for the C70 models which were delayed till 2003. The Denso 5 cylinder non turbo engines switched to Denso electric throttles for 2003.
Thank you for the advice but unfortunately this did not solve my issue. I charged my battery for 2 days and did like you said turn the key to the on position waited for about 90 seconds then repeated that process two more times just to be certain. I should have though software in a few weeks hopefully I will learn more from the codes being stored in the ECM as to what the issue is.

Is it possible that the throttle pedal sensor is now faulty? I may wind up having to get one from the salvage yard but I don't like just throwing parts at a problem unless I'm certain.

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Re: TCM/Accelerator Pedal adaptation

Post by abscate » Sat Jan 18, 2020 7:13 pm

A 1 amp trickle charger for 2 days will restore about 30% of your battery power

Put on on a10 amp charger all day.
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Re: TCM/Accelerator Pedal adaptation

Post by precopster » Sun Jan 19, 2020 2:18 am

You really need to read the car with a high end scanner or Vida/Dice. Rule of thumb with Volvos is they don't give accurate fault codes to low end scanners and the ELM327 adapters, though a ELM327 can usually clear 95% of codes on Volvos.

I seriously doubt a pedal sensor as they have an extremely low percentage of failure.
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