P0301 caused by bad ECM on 5th gen?

[ibexlatham]

Hi,

I dont post often because until recently I've never had many problems with my maxima...

I've got a 2000 Maxima SE 5spd with 194,000 miles on it and I recently had the A/C compressor seize up on me when I was at work causing it to not start. Since I was 40 miles from my house and figuring it was something simple and just plain sick of working on the car (I had just finished the clutch and trans and a bunch of other things) I had it towed to a shop to diagnose and possibly fix it. After they called me asking for $2300 to do the compressor, plugs, and starter I had them leave it apart and tow it to my house, I installed the compressor and put in new plugs, put the coils back on and finally got it started and it was running on 5cyls.

Now, I know the common response is "its the coil". I swapped the #1 and #3 coils and it stayed with #1, I then swapped the #1 plug with the #2 plug and it stayed in #1 cyl. The #1 plug didnt look like it ever fired when I removed it, no discoloration at all. I then disassembled the connector and got good voltage and ground at the red and black wires and the red/yellow wire was showing 0v. I performed the same check on the #3 cyl and there was about 1v (It showed this because the meter couldnt keep up with the switching rate I assume). I then checked from pin 21 at the ECM to the coil connector and the resistance was 0 ohms.

What I think happened was the shop probably shorted the ECM by checking for spark, probably used a spark tester that shorted to the red/yellow wire which I cant prove or get them to pay because they didnt work on it or see it run...

Is there anything else I should check before condemning the ECM?
Is it true the ECM is specific to '00 5spd, SE, 17in rims?
Is it also true that the car wont start and the dealer needs to program it after installation?
one site said I needed to change the IAAC valve and the TPS sensor, is this also true?

I know I've asked a ton of questions but I really need to get my car back ASAP as its been out of service almost all summer... it should have almost 200k on it but I've only been able to drive it about 500 miles since june...

Thanks,
James

[loystock]

You have done all the right moves. The Ignition Coil #1 terminals are as follows - Pin 1 (RED/YELLOW) is Base Bias to Power Transistor in the coil with signal coming from ECM, Pin 21; Pin 2 (BLACK) is Ground; and Pin 3 (RED) is Power. So you have verified Power, Ground and continuity of the RED/YELLOW (Striped) wire from Ignition Coil to ECM. So only 2 possibilities remain - the Striped wire is shorted to ground or Pin 21 from ECM is 'dead.' So verify that the Striped wire is not grounded then with engine running, check the voltage from Pin 21 of the ECM. When checking for voltage, measure from Pin 21 with respect to chassis ground. DO NOT USE THE ECM GROUND as it could damage the internal components. If there is no output from Pin 21, you have to replace the ECM.

Is there anything else I should check before condemning the ECM? - Check ECM Pin 21 output as above.

Is it true the ECM is specific to '00 5spd, SE, 17in rims? - The ECM discounted price are the same for Auto and Manual. Call NICO sponsor, IoS, to confirm from the link below.

http://www.infinitipartsusa.com/partloc ... atalogid=0

Is it also true that the car wont start and the dealer needs to program it after installation? -Your car is equipped with NATS (Nissan Anti Theft System) where the Ignition key IDs are stored in the NATS IMMU (Immobilizer Unit in the Ignition Switch assembly) and ECM. So if you replaced the ECM, it has to be re-programmed at dealer. Bring all your keys/fobs with you.

one site said I needed to change the IAAC valve and the TPS sensor, is this also true? - it's more of a precautionary measure as a defective (shorted) IACV actuator (stepper motor) will 'kill' the ECM. IIRC, the IACV coil resistance is 22-30 ohms. Refer to the link below for FSM (Factory Service Manual), particularly to EC (Engine Control) and EL (Electrical System) for detailed info.

http://www.nicoclub.com/FSM/maxima/2000/idx.pdf