Fried ECU's

OK, I have managed to fry two Honda CRX ECU's this season. First one was a 90 modified JE Import unit and second was a stock 90 ECU.

After the first one, figured it might just be the ECU chip. JE located the chip into another ECU and it was fine.

After the second ECU was fried this year, I am thinking it might be something in the car.

Basically, the ECU give a red light on all the time error code. When you look in the manual, Honda says if the red light is on all the time, replace ECU.

When this happens, the car struggles to run over 2500 rpm or under load.

So, any suggestions of items to check. I really don't want to put another ECU in without looking for something. $100 for an ECU and a trip to the paddock during a race really sucks!

Have you checked all the wiring harness for bare or frayed wires. What exactly is burnt? Does it run fine until it stops working? If it runs fine and happens under race conditions I would suspect a short of some sorts. i have never had a Honda ECU cook. God knows i have destroyed everything else at least once. If you need an ECu I have a chipped and unchipped ECU reasonable.

First of all, print off a wiring diagram of the connectors with where they go- a pinout. Check all the power and ground circuits first- you want to test for voltage drop, so for this test, use a large testlight, or even a headlamp bulb. Check all the connectors at the ecu to make sure nobody has stuffed a testlight into one of the connectors and spread the pins, causing a poor connection. DO NOT probe an electrical connection from the front- Backprobe only.

Next step is to look at all the circuits that are controlled by the ecu- injectors, evap solenoids, idle speed motors and so on. Check for resistance through all those circuits. For solenoids, it is best to actuate them for a while to see if resistance drops out of range when they get hot. You do have the factory service manual you take to every race, right?:cool:

Inputs from sensors are unlikely to cause trouble- no significant current flow through them, but its worth testing resistance on them , and if they are out of spec, have a look to see if they might be shorted to power or ground. Most sensors run on a 5 volt reference voltage- it should be right on 5 volts. If not, make sure one of the sensors isn't shorted to ground. Typical Dodge problem- crank sensor shorts, draws the reference voltage down.

Now for the thing you maybe should do first- a lot of these problems are caused by hamfisted backyardigans. Are you one of these?:rolleyes: Many many electrical problems I see are traced to a previous repair or attempt at rewiring.

If you can pop the cover off the dead ecu, you might be able to see a problem area on the circuit board, but its really tough to trace a printed circuit. If it hasn't actually burnt the board, theres no hope for that, but if the car still runs, and you can figure out what is actually not working correctly ( short duty cycle on the injectors, incorrect map reading....) you may have a clue of which circuit to trace.

Welcome to the simple and profitable world of auto repair.:(

You might try sending the dead one to Xenocron and have them check it out. It is like $35.00 for checkout and minor repair. More if it is bigger and they call first. They could tell you what the issue was and where to look for the fix.

Mike

Thanks for the input guys. Yes, I do have the manual and use it frequently. I was hoping to avoid getting out the wiring diagrams, but that looks like the next step.

I haven't made any repairs or modifications to the harness, but could have a short somewhere.

I like the suggestion of opening the dead one. I will see if I can find any burnt spots.

I'll keep you posted. Thanks