OMP Testing Question
 

Today I was helping a friend with his (new to him) FD.

It's throwing a code 27 (OMP) and tossing into limp mode whenever he gets on the throttle or up in RPMs.

I tested everything per the FSM and found only one thing out of spec, but that's if I'm reading the test correctly. Per the FSM, one of the terminals at the OMP connector (J, IIRC) should vary in voltage from 1.1v to 4.2v under acceleration. Parked, his stays exactly at .9v even when he revs the engine.

Is that sufficient proof that we need to change the OMP, or must we take it out for a drive and test that terminal under load as well?

Dave

I think that is sufficient to know it is not working properly. The voltage range of the OMP is quite similar to the TPS. If it isn't injecting oil by receiving sufficient voltage in coordination with the TPS then it goes into limp mode.

This seems like good info to know. Thanks.

IIRC, the OMP is strickly rpm based, so testing under load isn't likely to change things. But it's a PITA job to change them out, so if you have something that will show peak voltage it couldn't hurt.
FWIW, my car ate two OMPs. I have no proof, but a strong suspicion that the stock ECU was cooking the OMP sensor at WOT...which is where I saw the on-set of both CELs and subsequent limp modes. While it doesn't specify, I think code 27 does relate to the sensor. If you could figure out a way to check, or maybe someone else can confirm that before having to change a second one......?
I also made a short how-to thread a while back on changing out the OMP in the car that might be some help to your friend.

I did read your how-to, which I plan to refer to in detail.

I believe code 27 does imply the position sensor part of the OMP.

I'm wondering if it's worth pulling the turbos to do this. We've got work to do in that area anyway.

Dave

If you have to pull the turbos, that'll help alot as far as access. Be sure to get new copper washers and the 'O' ring from Ray.

Edit: In my first post I suggested checking peak voltage under load if you could...but of course you can't in limp. duh. :rolleyes:

I don't think it is load or RPM based. It looks to be TPS based. Peak voltage can be seen with the car off and the throttle to the floor (just like with the TPS).