1991 Q45 ECM ECU Replacement and Part Number Compatibility

[silverQ]

saw this list but many are missing

http://www.jimwolftechnology.com/wolfpdf/ECU-ID.PDF

can i use a different part number from mine or do i have to match mine exactly

is A18 A21 P20 9

for instance will 94 FED with 4WS, active suspension, TCS work in my 1991 base car

i read not to mix CAL and FED emissions

was looking on ebay but found a local yard through car-parts.com has one that says :

Elec Cont Unit (ECU), (RH kick pnl), from 11/93, FWS, w/o Full-Active susp;

w/o trac cont; Fed A18-B16-PB5 for $50

maybe even the newer computer is made better

-thanks

[Haitian_King]

If I remember correctly, the 94+ ECU's were 16 bit & the 90-93 were 8. For the most part, I think you'll be fine but I don't know much about Cal emissions and how they differ from other states.

[elwesso]

Basically you can interchange any 90-95 ECU and the car will run and drive 99% properly. If you run a 94 ECU in a 90-93 you may get a CEL because it will be looking for the EGR temp sensor.. The EGR will function properly, but it won't have the sensor there which may throw a CEL. That's the difference between Fed and Cal emissions in the 90-93. In the 94, the difference between Cal and Fed emissions was a couple extra sensors, but the ECU doesn't throw a CEL if they're not functioning (or present) therefore you can swap them out.

I've run a 94 ECU in a 90-93 before, and I seem to remember that it didn't always throw a CEL but it would on occasion. That is the *only* difference that will cause a CEL based on a ECU swap either way.

You will also get a secondary TPS code (but no CEL) if you use a TCS ECU in a non-TCS car. If you put a non-TCS ECU into a TCS car, the TCS will not function properly.

THEREFORE, when we program the NICO ECU's we program all of them for Federal Emissions, and TCS. The only downside is that the non-TCS cars get the secondary TPS code but hardly anyone ever checks ECU codes and it doesn't throw a CEL, so it's largely not an issue. In my case, we ran into more issues making sure that people specified TCS or non-TCS, so we eventually decided to program everything with TCS that way everyone was covered.

[silverQ]

Hello,
My old ECM was A18 A21 P20 9 and got a replacement from ebay number A18-B16 P93 4E. Auction read "INFINITI Q45 ECU 93 94 95 A18-B16 P93 ECU A18B16P93 ECM ENGINE COMPUTER # 3314". Problem is the new one has the red light when I turn the key like it should but does not cycle the fuel pump. Put the old one back in and fuel pump cycles properly, pressures look fine. In your opinion is this replacement ECM a bad unit or is it more likely an incompatibility between the differrent part numbers?
Thanks,
-silverQ

[Q451990]

I don't see that one on the list you linked at all... but it does show up in a lot of searches as one for the 94 Q45. Let's back up a little... why are you replacing your existing ECU?

Heath

[silverQ]

I don't see that one on the list you linked at all... but it does show up in a lot of searches as one for the 94 Q45. Let's back up a little... why are you replacing your existing ECU?

Heath

car seems was running unusually rich and then it stranded me a month ago. tried to start it a few times ran for like 20 seconds then stalls out flooded. more info in this thread where-can-i-get-my-car-serviced-in-317- ... 66355.html

thanks for the help

[silverQ]

reseated the new ecm's connector it is now cycling the fuel pump but am having the same symptoms as before. i'm getting spark and getting fuel, motor is hitting but won't sustain itself

anyway seems the newer ecm is working just not the problem

[elwesso]

I think we could have told you the ECU was not the problem. They almost always work 100% or not at all.