ultradef

Please do, it would be a huge service to the rotary community. Even though its too late for me...I've had so much trouble with the OMP and ECU that I just "had" to go standalone.

Actually, the cost of a remanufactured ECU and a used OMP isn't much less than a good, used standalone (if you can find one). Its just everything I bought on top of the standalone (injectors, boost controller, clutch, etc) that made it expensive. Anything to get rid of that damn OMP at this point.

Albert257

btracer02 and YearsofDecay, where in PA do you guys live?
And where does that guy in York who knows about OMPs and ECU's live?
I am very close to York.
Let me know if you find anything out about that! Thanks

RX7.0

Do what you can.... we'd all appreciate it!
To do my part, There is an electrical engineer at my work that I hang out with sometimes.... I told him about the situation. He (very un-enthusiastically) agreed to look at the pump and ECU (if I can't get my car out of limp mode this weekend) with the intention of finding a way to fool them. He would then draw up the plans for me to do myself... an I would share them, of course

This plan is very tentative and assumes that he will have the time.
So don't count solely on me.

inflatablepets

Anyone know?

ultradef

It would still be a possibility for the OMP stepping motor to fail and cause the car to be in limp mode, even if the OMP is not installed on the engine. When you tie up the OMP, you must still leave the electrical connections to the ECU. When the electronic stepping motor or sensor fails, that is what blows the ECU. You cannot disconnect the OMP from the ECU or the car will remain in limp mode. Removing and tying up the OMP has no benefit except for the ability to run premix.

ibmiked

One of the things I discovered was very important was to inspect the OMP plug at both ends, first the white 6 prong connector that plugs into the harness, and second the grey end that plugs into the OMP itself. Check for corrosion, and run a continuity test on them. One of the OMP's that I got that was "bad" turned out to just have corrosion on the grey connector plug. Even with a good OMP and a rebuilt computer, I'm still trying to figure out why every 10 minutes I go into LIMP mode and get code 27 (fixable by turning off the car). I think maybe the rebuilt ECU just isn't any good. Go for a verified working used unit. Just to be safe, I grounded the OMP to the firewall since mine is zip-tied to the strut tower, and might need a ground since it isn't bolted to the motor anymore.

My .02 cents

ilike2eatricers

Just to verify. For all those with an s5 OMP who had their ECU go out on them, how did you confirm the ECU was dead? Honestly, I'm not sure if my ECU is bad but I swapped out both new ECU and OMP just in case.

inflatablepets

Right, that's what I thought. I'd take it off except for the limp mode thing. Other than premix, I see no benifit of tying it off the side, since it can still break and smoke the ECU. Does anyone know what exact part it fries on the ECU? Possibly a 10 cent resistor or diode maybe?

ibmiked

I've been told it's the "4-10 diode" if that makes any sense to anyone.

ultradef

I know my ECU is dead because I opened it up and there is a big black spot on the circuit board where something blew up. I also replaced the OMP twice, but I could have bought two bad OMPs, especially with my luck. I would take the outer case off the ECU and take a look at the circuit boards and look for fried components like mine.

ilike2eatricers

I already did that and they were no burns. I just replaced both the ECU and OMP with known working units and the car runs fine now.

johnmasters

Talk about a thread resurrection...

I realize this thread is over 5 years old but I am currently dealing with this problem and this is the best thread I could find regarding the OMP frying the ECU.

I have several questions but wanted to start with this one.

I understand that if the stepper motor acts a a resistor that it makes since how the ECU gets fried but, how is it possible for a fried ECU to fry a good OMP?

My situation...

Car is running fine.
Water pump goes bad.
remove OMP in order to remove water pump housing.
OMP is real grungy and missing the little plastic black electronic cap
Put everything back together, works great but,
now goes into limp mode with code 27
replace OMP with known good OMP and still going limp with code 27

Questions... if the ECU fries, is only the OMP circuit affected or will the ECU start misbehaving in many more ways and throwing many more codes?

If the ECU is fried and pre-mix is acceptable would installing the $120 Rtek work as a bypass?

If you replace the OMP but DO NOT disconnect the negative in order to clear the codes, will the car continue to go into limp mode?

Does anyone have an S5 n/a Vert ECU?

Thanks in advance!
john

jackhild59

iTrader: (7)

Here is the best thread regarding this problem: https://www.rx7club.com/2nd-generation-specific-1986-1992-17/s5-mop-ecu-failure-diagnosis-710938/

The Rtek will prevent the problem if you get it before the ECU is burned.

There is apparently no reasonable way to mimic the MOP/ECU/TPS relationship without throwing the ECU into limp mode.

My MOP burned out my ECU. I replaced my vert ECU with a California N/A ECU and did a full diagnosis on a used working MOP. It all works just fine.

Good Luck!

johnmasters

Thanks for the link. I missed that one.

So, did you use the California convertible(n352) or just the California(n350)?

jackhild59

iTrader: (7)

n350.

That's my best shot at 'going green.'

-Crushing the Ecosphere one Barrel of Oil at a Time

RX7 RAGE

iTrader: (22)

I just pulled my s5 ecu out and was wondering if this is the correct one I pulled out. It came from the driver side kick panel. I believe my OMP also fried my ecu and I'm going to replace both

HAILERS

Show us a picture of the ECU and we'll tell you if you have the right part or not.

jackhild59

iTrader: (7)

That's not an ECU. (as Hailers also noticed!) The ECU is under the passenger side floorboard. Remove the cover, unbolt and unplug the ECU. Crack it open and you will be able to clearly see the burned circuits on the circuit board.

jjcobm

iTrader: (18)

DSM Parts????

HAILERS

The jpg seems to be of maybe........a cruise control unit for series five or some other object. All parts are more or less shown in the FSM. FSM is downloadable on this site from the FAQ thread.

johnmasters

jackhild59, I dont mean to be redundent but I have found a good deal on an n350 and I wanted to confirm that your convertible top works fine with the 350. If so, whats the difference between the vert and non vert ecu? I wonder if there is enough of a weight difference to warrant different tuning?

bac22

Ugh...I'm having this problem now, but do you get codes when this happens?

My check engine light comes on, but I'm not getting any codes, so I'm not sure my OMP is bad.

jackhild59

iTrader: (7)

Yes, it runs fine.

johnmasters

I am getting code 27.

johnmasters

While we are on this subject and since this really hasnt been covered with any detail, can anyone answer...

I understand that if the stepper motor acts as a resistor that it makes since how the ECU gets fried but how is it possible for a fried ECU to fry a good OMP?

I ask because somewhere on the forum a long time poster made a comment that not only a bad omp can fry the ecu but that the fried ecu can also fry the new omp. Is this, IN FACT, correct?