Throttle actuator question

hcritz · Post by **hcritz** » 05 Jan 2016, 11:37

I'm still battling some sort of crazy electrical issues with the 2002 V70 T5.
I'm getting some TPS codes that I can't delete and reduced power and engine management readouts on the dash.
I have pulled the throttle body and placed it where I can watch the action and with the key on it moves very slowly to wide open if I push the accelerator pedal to the floor. Of course the engine is not running at this point...just ignition in the run position. Does anyone know if this is a normal condition or do I have a Throttle body issue...or possibly an ECM failure???
I've spent a LOT of time trying to get this thing to run correctly after the engine swap. ANY help will be greatly appreciated.
Not sure where to go next...no dealer here.
Thanks!
Ed

sparky65 · Post by **sparky65** » 05 Jan 2016, 16:30

Are you still using the original ETM or was that swapped too when you changed the engine?

hcritz · Post by **hcritz** » 05 Jan 2016, 17:28

Hey Sparky...
Yes...I installed the original ETM on the new engine. Today I've been checking wires and grounds and haven't found anything amiss yet.
Here are the codes I'm getting:
p2126
p2121
p0073
The latter is an air temp issue...which I'm pretty sure happened from a backfire in the intake tube.
Not sure if you have seen my earlier post ...here is a link to that if you have time. https://www.matthewsvolvosite.com/forums ... =9&t=73672
I'm about at wits end here...I did go ahead and order both ECMs not sure when they will arrive and I may be a little hesitant to install them until I'm sure nothing else is wrong so I don't fry one of them!
I'm a very anal mechanic...every clip and tie wrap has to be back in place etc...so this should have been an easy job...just a lot of bolts to take out and put back...the wiring on the car is relatively straightforward to remove and re-plug. I did remove the harness with the sub-frame.
Any help will be greatly appreciated!!!!
Thanks,
Ed

sparky65 · Post by **sparky65** » 05 Jan 2016, 18:46

Ed,

First off, the p2126 p2121 are AP related codes not ETM/throttle position.

P2121 ECM‑9540 Accelerator pedal (AP) position Faulty signal, sensor, digital signal
P2122 ECM‑9530 Accelerator pedal (AP) position Signal too low sensor, digital signal
P2123 ECM‑9530 Accelerator pedal (AP) position Signal too high sensor, digital signal
P2126 ECM‑9520 Accelerator pedal (AP) position Faulty signal sensor, analogy signal
P2127 ECM‑9520 Accelerator pedal (AP) position Signal too low sensor, analogy signal
P2128 ECM‑9520 Accelerator pedal (AP) position Signal too high sensor, analogy signal

Did you also say both ECMs? There is only one. the other is the TCM. These are not going to be plug and play either. Dealer programming required to replace these. In my opinion, the Volvo ECM is a pretty robust and reliable piece. I'd look into the Accelerator Pedal codes first if I were you. If the car wasn't coding for these before the swap, I'd be shooting wires and connections first before replacing parts.

hcritz · Post by **hcritz** » 05 Jan 2016, 19:37

Thanks Sparky...
There were no errors before the swap and all of this seemed to occur while trying to sort out the hard starting issue.
Not sure if you followed the other post but I had an issue with the crank position sensor that I am still not sure why occurred
Nothing inside the car was moved but will definitely check the Accelerator pedal and wiring.

Yes...I found a pair, the ECM for Engine and the TCM as a pair.
what led me to suspect the ECU is that I can't erase the error codes. The CEL is not on with the engine running, but will stay on just in the run position. I get the three codes and if I try to erase them...my reader says two remain...but all three are still there. Possibly it's reading the throttle/pedal even with out running? I may be incorrect but figured the TCM would get some sort of signal from the throttle as well or share info from the ECM.

I wasn't aware they had to be programed! TYPICAL! Even the window switches do! The ECM/TCM are used units from a matching car/engine combination if that's any help.

Several things I have found today in checking...The throttle is non-responsive with the car in gear and your foot on the brake...maybe that's normal. Also, I have had a few occasions when starting the car the pedal in non-responsive...restart and it works.
This car does Not have the Magneli Marreli unit. It's the motor driven one with two sets of carbon resistor tracks which seems to be much simpler.

I am about at the point of removing the engine harness and trying to ohm out each wire. All connectors have been checked, rechecked and rechecked again.
Thanks again!
ED

Post by **precopster** » 06 Jan 2016, 04:40

If it's the Bosch unit I would remove the connector from the throttle and recheck the tension on the pins. Often a faulty throttle connection will read as a faulty accelerator pedal; the 2 are so closely tied that poor resistance in one unit will cause the other to code. The accelerator sensor is a Hella unit and is known to be to be extremely reliable therefore if the Bosch unit is coding after the swap it's more likely the pins on the throttle were disturbed.

If you were reading the car with Vida you might get some extra info such as brake pedal position sensor. This can also cause no throttle during brake depression. This sensor is on the brake booster with a 2 pin connector.

hcritz · Post by **hcritz** » 06 Jan 2016, 06:38

Thanks Mike...I will pull the connector apart and tighten the pins and also check the pedal unit.
Am I correct in assuming that the throttle plate should move in unison with the pedal? Mine is working in a very delayed fashion.
Not sure on the theory of how the system works, but I figure it reads both resistor tracks and compares them as a safety check and if one is different it goes into a safety mode??? This is just a guess on my part.

Post by **precopster** » 06 Jan 2016, 13:12

I know the Magnetti ones directly follow the pedal even if they're coding. Can't say on the Bosch ones. Stick with the throttle or get another pedal assembly from wreckers and plug that into the harness without removing pedal.

Pretty much what you said is correct thouigh impedance of throttle pins can fool system into throwing pedal codes.

The Hella pedal units are best left intact. Try plugging/unplugging the pedal connector to scrape off any corrosion.

hcritz · Post by **hcritz** » 06 Jan 2016, 15:23

Hey Mike.
I spent all day ohming wires from the sensors and throttle body back to the ECM connector. All the wires appear to be Ok. Checking for grounds and shorts as well. The three chassis grounds look good ... I'm still trying to trace the one on the block back to the ECM connector. More work on that tomorrow. I did take the throttle body connector apart ( one pin at a time) and cleaned and tightened the connectors as best as I could. They are pretty tiny.
I took the throttle body apart and checked again...I'm getting smooth ohm changes on both circuits there as I open and close the throttle.
I did take the Hella apart. It's an interesting device. I'm not sure I quiet understand how it works. It's not a carbon resistor and wiper assembly like the throttle body. There don't seem to be any parts that make contact inside so no evidence of any wear etc. Connector looks clean and solder joints look good. I'll ohm the wires from the pedal to the ECM plug tomorrow...will have to make up a long extension for my meter. I should also have my new ECM tomorrow (Used One) .
I don't fit under the dash of that thing very well!!! LOL
Thanks for your help...I'm really tired of working on it!!!
Should have been an easy R&R and turned into a nightmare!
Thanks again,
Ed

Post by **precopster** » 06 Jan 2016, 16:58

The ECM and TCM are married by Canbus to CEM so they won't allow the car to start because they each have an immobiliser section.

For argument's sake you could connect the ECM and see if the throttle codes will clear but that's as far as you will get without sending it away with the original for cloning.