I have a 1998 Honda Accord, 3.0 V tec auto I bought with issues, (wouldn't start). Some history. Previous owner was persistent that the fuel pump was the issue. I started digging into the issue and the main relay was not turning on. I also couldn't link with any type of reader to the ECU. After more digging I also found I was not getting any injector pulses. I deamed the ECU was bad. Now here is my question, the ECU that was in the car has part # 37820P8CĄ513M5. I have a different good ECU but not the same part number. Just trying to get the dang thing to run. With the new ECU installed, I can link to it and the main relay comes on so the fuel pump runs and builds pressure. Currently the passkey system is locking me out so it still won't run. Going to get the key programmed tomorrow and see what happens. The number on the other ECU I currently have installed is 37820P8CL51. Now I understand the 37820 is a Honda ECU, the P8C is the 3.0 engine and the A51 and L51 codes are for the transmission. I can't find anything as to what the 3M5 mean. Also not sure if the trans will work properly or what all can be flashed when I link to it tomorrow. I did find an ECU with the correct part number and will more than likely get it and teach the key to it but can anyone fill me in on what the 3M5 mean and the problems I may encounter with the ECU I currently have installed. I should be able to make it run once I train a key tomorrow, right?

 

I can't just enter OEM part numbers on the hondapartsnow.com site, where it will tell me the vehicles that fit.

I typed in 37820P8CĄ513M5 on Ebay. It looks like this is the PCM for a 4-cylinder accord based on the Ebay description, so this probably won't get your vehicle to run.

37820P8CL51 is showing as a discontinued part on the hondapartsnow.com site. Usually Honda will update the software to say version 2, then the new part number will be 37820P8CL52, where the 2 means version 2. Go to hondapartsnow.com and use your VIN to determine your vehicle, then find the OEM part number for your PCM. It is under electrical, control unit cabin.

They usually list the original part numbers and the newest revision as well.

 

I did go to the Hondapartsnow website and did some digging and found that the P8C is for the 3.0 Vtec. My buddy came over today and we were able to change the VIN for the ECU and able to teach the key. So now is where it got interesting. Everything linked fine and once the key was taught we started the car. Mind you the car hasn't ran since August. It rolled over 3 times and started right up and ran just as smooth. First time I've heard it run. Snappy throttle, sounded nice. It warmed up and threw 2 codes, PO108 and PO135. Map sensor high voltage and HO2S S1 heater malfunction. After the car was running for about 3 minutes the idle started to surge. Not a huge deal, figured it could be the MAP sensor causing this. After it ran for about 8 minutes the idle went higher to about 2500 and the car just died, lost communication with the programmer and I'm back where I started with the original ECU. Main relay won't come on for the fuel pump. Unable to communicate with any scanner or programmer and no injector pulses. What in the heck would take out an ECU in 8 minutes? I have checked all grounds in the car. Is it possible a shorted map sensor could take it out? I have never heard or seen anything like this scenario.

 

A short from the map sensor would send full voltage/amps to the ECU and could fry your ECU. If you know the pins for the map sensor, you may be able to trace the ECU board to visually or electrically verify a component on the board was overheated/fried.

Measuring the resistance across the power and signal out of the map sensor may determine that it has a dead short. The issue could also be in the wiring and not the sensor, so follow along the harness for any signs of damage where the harness casing could have worn due to vibrations or possible corrosion. You definitely want to figure out the electrical issue before trying a different ECU.

 

I hear that. I have a full wiring schematic I printed off last night and will start going through it tonight. I have another map sensor as well. I couldn't see or find anything obviously bad on the original ECU. I haven't pulled the replacement yet. I was a little discusted last night. I'll keep digging and see what I can find and update once I get to a new place or find the solution. At least I can find ECUs for that thing for around $40 used. It's just funny how it just died and was done in 8 minutes. Didn't even get a chance to do a trending map for the input signals. I just thought this one was kind of a rare senario so that's why I'm on here. Hopefully this thread can help someone one day.