ETM repair didn't work, any ideas?

FoxClubNiner · Post by **FoxClubNiner** » 27 May 2016, 13:42

Hey all,

I have a 2000 S80 T6. Last week I pulled code P0121 from it after it went into limp mode. It has a check engine light on, service light, and a message that says engine service needed.

I installed this contactless sensor part:
http://www.ebay.com/itm/271642938195?_t ... EBIDX%3AIT

I started it up and it still has the same issue. I cleared the code and P0121 still comes back and the car remains in limp mode.

Did I miss something? This shouldn't require a program right? Are there any voltage checks I can do?

Thanks for the help!

Post by **precopster** » 27 May 2016, 16:42

If the unit starts up properly with ignition in PosII by clicking once then singing for 6-10secs then clicking back off then the voltage is fine; no calibration needed.

Because you've scanned with a generic scanner you've probably missed that it was a signal missing from one of the two sensors. Older ETMs are famous for totally losing one of their outputs from the control board. The contactless sensor is at the INPUT stage so doesn't help.

FoxClubNiner · Post by **FoxClubNiner** » 31 May 2016, 11:07

precopster wrote:If the unit starts up properly with ignition in PosII by clicking once then singing for 6-10secs then clicking back off then the voltage is fine; no calibration needed.

Because you've scanned with a generic scanner you've probably missed that it was a signal missing from one of the two sensors. Older ETMs are famous for totally losing one of their outputs from the control board. The contactless sensor is at the INPUT stage so doesn't help.

I'm a little confused because I thought ALL sensors were inputs and actuators were outputs. I couldn't find a wiring diagram for my ETM. That would certainly help me.

I plan to back probe the wire that goes from the sensor to the computer and check voltage when I move the throttle plate by hand. Hopefully that reveals something.

I'd purchase a used ETM off ebay if I knew if it was compatible without a reflash. I'm ready to be done with this project.

Post by **precopster** » 31 May 2016, 15:35

The sensors on either side of the ETM are potentiometers. They have a 7V input and lower this down to between 1.35V at home position (idle) and full deflection of the throttle which is around 6V.

The idle voltage is available when the unit is separately powered on the bench with a 12V supply to allow the unit to initialize and then tested between pin 1 and 3 on potentiometer 2 (the Sacer side) and pin 2 and 4 on the other side which is potentiometer 1. If the voltage is under 1.25V and over 1.55V the unit won't start. Did you properly lift and separate pin 2 of the Pot 1 sensor on the black wire side?

This voltage is then fed into the ETM's logic board housed under the aluminium plate for further lowering to between 0.8V at rest and around 2V at full deflection. These outputs are only available for measurement at the cable by tapping into the blue/red and yellow/green wires at the plug. These are sensor 1 and sensor 2 outputs.

The other colours are purple and pink for the twisted pair to Canbus and green and brown which are power and chassis respectively.

There are no circuit diagrams of any modules on Volvo cars; only wiring diagrams of vehicles. Hope this helps.

FoxClubNiner · Post by **FoxClubNiner** » 01 Jun 2016, 09:39

Key on engine off noise test:

ETM voltage test:

green: 12V
brown: .2 Ohms
blue/red: 1.045V
yellow/green: 0.006V

So If I understand correctly, the blue/red and yellow/green wire should read the same voltage (key on engine off) and should change voltage when I move the throttle plate by hand (0.8V at rest and around 2V wide open).

Since I only have the blue/red wire with voltage the computer sets the fault and goes into limp mode. I believe I installed the kit correctly. It wasn't hard, I just followed the PDF instructions. Does this mean I need a ETM now?

I thought about splicing the blue/red and yellow/green wire together to fool the computer but I don't think it would help because the voltage doesn't change when I move the throttle plate.

Post by **precopster** » 03 Jun 2016, 14:49

It probably has an internal problem where it doesn't process one of the inputs. I've seen it many times. To be certain before concluding this are you getting around 1.35V at both potentiometers as I described above?

FoxClubNiner · Post by **FoxClubNiner** » 07 Jun 2016, 17:06

precopster wrote:It probably has an internal problem where it doesn't process one of the inputs. I've seen it many times. To be certain before concluding this are you getting around 1.35V at both potentiometers as I described above?

I didn't measure them before. Could you educate me on how to measure the potentiometers? I only saw the one 6-pin connector that comes off the ETM. That's how I got all my voltage checks.

Ok, so I ordered a used ETM off ebay for my model/year and put it on the car. Right off the bat this ETM would "sing" on key position 2 when my old one wouldn't. So that was a good sign. I re-checked all the pins on the ebay ETM the same way I did before and to my surprise I got the exact same results. I expected the voltages to change when I moved the throttle plate by hand but they didn't. That confuses the hell out of me. But whatever.

Anyways, the car has been driving fine for 2 days now with the used ETM I bought on ebay! Hooray! Now to tackled the oil leaks at some point (turbo return lines and PCV).

Thanks for the help!

Post by **precopster** » 08 Jun 2016, 03:40

The pic doesn't show where pin 2 and pin 4 is on the non-Sacer side but you should get the jist from this

FoxClubNiner · Post by **FoxClubNiner** » 08 Jun 2016, 07:37

precopster wrote:The pic doesn't show where pin 2 and pin 4 is on the non-Sacer side but you should get the jist from this

Thanks, that's a really helpful picture! Is that image from a larger set of pictures? The directions I got for my sensor weren't this good at all.

Post by **precopster** » 08 Jun 2016, 17:38

That's because I wrote these

They were added to a really large thread in Don's ETM Room: https://www.matthewsvolvosite.com/forums ... 12&t=38504

This pic is pretty much all you need.

Also knowing that voltages at the sensors need to be between 1.28 and 1.45 with voltage applied and the unit at rest