mattdavispv9

iTrader: (7)

The 7 was just acting up. First the check engine light came on. I ran the codes and it brought up a lot of problems. One of the codes was for the double throttle sensor... I fixed that and ran the codes again. All the codes were gone. The car was running good and then all of a sudden the check engine light cones on... Now the only code is for the omp...
Code 27. Short circut, stuck omp sensor or manfuctioning ecu. The car has been running well untill I fixed an oil pan gasket leak. And then all of a sudden the car is acting up. I need some help. Thanks

Sgtblue

iTrader: (16)

I doubt your OMP issue has anything to do with sealing the oil pan.

Was the on-set of the latest CEL right after a WOT event?

bumpstart

usually its the sender all covered in oil from leaking OMP pipes
( but dont rule out a bad join at the plug by the thermostat )
- remove the OMP, separate the sender and clean it in electronic solvent cleaner
then test its output with a multimeter, should be even all the way through the stroke
( IIRC the range to about 2.5K ohms , half that of the TPS output )

i have had a few of these apart on the bench whilst helping design a stepper controller for them
and i recall a couple of them had suss senders,, and they all came good with a clean

only one unit had a fault in the motor winding resistance,, and was not repairable

--- makes you wonder about all them units that have failed,, that your dealer insists you must exchange them for new ones

mattdavispv9

iTrader: (7)

i know, haha.. just a coincidence

i was at stop sign and i boosted to about 9psi in 1st gear and then to about 4k in second gear... not WOT but i did get on her... last night i reset the ecu because i think its just a bad connection or sensor, and i drove 17 miles without any problem... and then code 27 came on again. i will be pulling motor to check out everything... thanks guys

Sgtblue

iTrader: (16)

I've had the same code twice on two different OMPs within a couple of months... but with the same stock ECU. Both times all the continuity and resistance checks were fine, but a persistent code 27. I have no proof and this is just FWIW... but I began to suspect the ECU was responsible. Each time it occurred it was after a WOT episode. I'm a pretty conservative driver, so I don't go WOT all that often on the street. But it started each time almost immediately after WOT.....a voltage spike that was too much for the sensor? IIRC, they're only a 1 to 5v range.
I installed a third OMP with a PFC and haven't had issues since...same (albeit simplified and re-insulated) engine harness. I regularly do a sensor check from the commander and the third OMP is still going strong....~ 3 years now.

ttmott

iTrader: (1)

The OMP is positioned by the ECU based upon engine load, not RPM. As engine load increases the ECU evaluates engine RPM (this is a factor on the oil quantity injected), manifold pressure (PIM), and TPS voltage and sets a pulse modulated value to the stepper motor in the OMP which combined with the OMP rpm( driven by the engine) injects a specified oil quantity. The ECU will expect validation that the stepper motor is correctly position; this is provided by an integral potentiometer inside of the OMP. The ECU provides ground and +5VDC to the OMP pot and a biased value is returned to the ECU; the value depends upon the position the stepper motor has it set. Most failures in the OMP is the potentiometer but one never knows until it is removed and tested. The best test for a factory ECU is to take a voltage measurement (have a passenger monitor a VOM) under varying load conditions. Take the measurement from ECU pins 3A and 4D. Below is a chart that will provide expected values at given engine load conditions. This will isolate if there is a problem with the ECU or somewhere from the ECU to the OMP.

Sgtblue

iTrader: (16)

As I recall, both WOT episodes correlated with my CELs were in 2nd or 3rd gear....heavy load.
There was no motivation for me to test the stock ECU since I had already purchased a PFC by the second CEL.