OMP Testing (FSM)
 

Can anybody tell me is this is correct. Where is says:

"Is the resistance of terminal (Vo-E) and (Vo-Vc) as specified?"
"Resistance: 0.4 - 12k ohm"

If Im reading this correctly, I have to measure the resistance between (Vo-E) then measure the resistance between (Vo-Vc) then add the two together.

So I did so and got 1.692 and 0.737 and together that came to 2.429k ohm

Now, Im wondering if the fsm is correct when it says "0.4-12k ohms", but im thinking it should be "0.4-1.2k ohms" because 12k ohms seems like a lot, correct me if im wrong

any help on this would be greatly appreciated thanks

What are you trying to do? Is the omp showing out of spec? If you have a power fc or almost any other standalone computer you can monitor the omp voltage.

This test would mean the resistance as taken between the two terminals. One probe on Vo-E and the other on Vo-Vc.

I am trying to find out what is wrong with my car, I think I might have an intermittent short somewhere in my harness because I keep getting omp codes 26 and 27.

I stored my car over the winter in my garage and before I stored it i was also getting these codes so i swapped out the omp with a spare one I had, drove it for a couple of months (with the ecu loose on the floor) then stored it for the winter.

I just took the car out of storage couple weeks ago, drove it for a while then decided to bolt up the ecu and the metal wiring harness cover. Took it out for a drive and "LIMP MODE". Pulled the codes and what do you know 26 and 27.

Now im checking all the omp values and wiring again trying to figure out what wrong

Also I dont have a PFC just stock ecu

Terminal Vo, terminal Vc and terminal E and three separate terminals

I think the sentence is not stated clearly, and you are meant to take two separate measurements. It's possible that the range could be .4k ohms to 12k ohms. Who knows for sure but those terminals are for the position sensor part of the pump, and they could have a wide range of signal.

So how do you shoot the connector for ohms?

IIRC the connector is located near the base of the front engine hook/loop, behind the alternator.
If it helps I think thats your connector just to the right of the hoist loop.

Attachment 605131

FWIW, "Vc" is power to the top of the control potentiometer, as seen in the schematic on page Z-32 of my 1994 FWM. "E" is the ground return of the pot. So the total resistance of the pot is terminal Vc to terminal E. That is fixed, and the manual says it should be between 1 and 2 Kilohms. Terminal "Vo" is the wiper of the pot, or the "output." Resistance from Vo to E can theoretically vary only between zero ohms and the fixed value between Vc and E. The FWM says it must be between 0.4 and 12 Kilohms. But anything above the fixed value between Vc and E is impossible (see the schematic on page Z-32).

Say the Vc to E resistance is 1.5 Kilohms. Then the Vo to E resistance cannot be greater than 1.5 Kilohms. Depending on where the pot's wiper is sitting on the resistance winding of the pot, it can only be that value or lower. The FWM's lower bound of 0.4 Kilohms is probably right, and if lower, the pot assembly probably has a problem. But anything higher than 1.5 Kilohms indicates a very high wiper resistance and is also a problem.

Ok thanks so my Omp is good but my ecu harness seems to be the culprit, anyone know how to test it, I swapped ecu and still same problem so ecu isn't the prob I think the harness is