Sacer TPS fail

Arnexas · Post by **Arnexas** » 04 Mar 2020, 02:53

I have installed Sacer TPS around 6 months ago in my Volvo S80 2.4 petrol. It was fine for whole time until few days ago. As I was driving, it looked like the wind pushed the car back, but as I tried to accelerate a bit, it wouldnt accelerate at all. I have stopped the car and the revs started jumping randomly from like 600 to 3000. If I pressed the throttle pedal, it would go to 3k and sit here for like 5 seconds. After restarting the car, it ran fine for a while. If it adds any sense, it was a foggy morning. Also, I have found out that cruise control was working / not working randomly. If the brake pedal is pressed - throttle pedal is ignored. Starts struggling at around 3-4k rpm. No error messages appears on cars computer. Also, there is a delay in acceleration. Connected VIDA - the only error is ECM-91F0. Cleared the code and it apperead instantly. Today I started the car, it looked like the problem disappeared - cruise control switches on, throttle responsive even if brake pedal is pressed. So as I was walking around the car, I heard something like misfire and instatly went to investigate - problem appeared again. It was not hunting at idle this time. Possibly, this whole problem appears only when the car gets up to over 50-60 C temperature, as the engine was still not at working temperature, or it could be just coincidence. I have taken out the TPS, opened it, and it looks fine - my soldered contacts for Sacer side is still connected, the black wire going to the other potentiometer is also connected. Checked the voltage - still the same as before (1.39 V). MAF sensor is also working correctly - checked it with VIDA and multimeter - it increases with higher rpms. What could possibly be the problem?

Post by **RickHaleParker** » 04 Mar 2020, 10:13

1. Clean the battery terminals.
2. Have the battery bench tested.
3. Count the number of cylinders in the engine.

Arnexas · Post by **Arnexas** » 04 Mar 2020, 10:50

RickHaleParker wrote: ↑04 Mar 2020, 10:13 1. Clean the battery terminals.
2. Have the battery bench tested.
3. Count the number of cylinders in the engine.

Thanks for reply, I'll try to do that. The engine has 5 cylinders. I have tried starting the car and connecting VIDA again after resetting the errors and leaving car for few hours. It started with the same problem because I forgot to connect the MAF after cleaning. After connecting it, everything was fine - responsive to throttle when brake is pressed, until the engine got at around 50-60 and then problem appeared again. It happened in the morning also - that means it is not just a coincidence - the problem appears when engine is warm.

Also, I have checked the battery terminals as the car was starting - it dropped at around 10 V. On idle its around 14 V. ETM fuse in engine compartment has the same voltage as the battery, so no voltage loss here.

I have checked MAF readings from VIDA. MAF reads around 4 g/s on idle when cold. As the problem appeared (engine got hot), it was flactuating between 3 - 3.8 g/s.

I suspected the battery as it was not holding any voltage (11.5V after few minutes when car is turned off). But why would the problem occur when the engine is hot? It's constantly 14V anyways, as alternator is charging the battery.

Post by **RickHaleParker** » 04 Mar 2020, 11:11

Arnexas wrote: ↑04 Mar 2020, 10:50 The engine has 5 cylinders.

1999 - 2002 AME S80s where all six cylinders. Either 2.8L, 2.9L or 3.0L. Your profile says 2001 and you are waving the United States flag.

ECM-91F0 is set along with other codes unless it is an error due to low voltage. When ECM-91F0 is set, the accelerator pedal position is ignored when the brake pedal is depressed.

14V is pretty much pegging the charging system. Electronics operate off power not voltage. Some of the circuits maybe getting deprived of current because the battery is drawing most of the current from the alternator and supplying no current. Power = Voltage * Current.

You could say the defective battery is sucking the electrical system dry.

Post by **abscate** » 04 Mar 2020, 14:27

I suspected the battery as it was not holding any voltage (11.5V after few minutes when car is turned off). But why would the problem occur when the engine is hot? It's constantly 14V anyways, as alternator is charging the battery.

That battery is dead dead dead/

Unlike the 1960s, when everything was analog, when a car battery goes now, it creates all kind of havoc with the electronics

Post by **RickHaleParker** » 04 Mar 2020, 14:44

abscate wrote: ↑04 Mar 2020, 14:27 That battery is dead dead dead/

11.80V is dead. 11.2V is warmed over death.

Arnexas · Post by **Arnexas** » 06 Mar 2020, 14:30

RickHaleParker wrote: ↑04 Mar 2020, 14:44
abscate wrote: ↑04 Mar 2020, 14:27 That battery is dead dead dead/
11.80V is dead. 11.2V is warmed over death.

I have changed the battery - looks like problem disappeared, but cant erase the error with VIDA. After erasing, it comes back. Accelerator pedal is also ignored when brake is pressed.

Post by **RickHaleParker** » 06 Mar 2020, 15:01

Arnexas wrote: ↑06 Mar 2020, 14:30 I have changed the battery - looks like problem disappeared, but cant erase the error with VIDA. After erasing, it comes back. Accelerator pedal is also ignored when brake is pressed.

The information you need to trouble shoot this is in VIDA under DTC ECM-91F0 information.

Check the voltage to the ETM. Check the ETM software version.

There is a ETM software upgrade that corrected false errors by increasing detection time from 0.13 seconds to 10 seconds.