Jovic82

Hi everyone,

I have a JDM 96 type RS which is doing the most random of electrical faults.
Every other start of the engine , the abs light comes on and the heater controls completely stop working (no lights or anything) and then the next time it all works ok.

Things I've checked and changed so far, tacho repaired , abs all good, Cpu 2 repaired , ecu swapped with another known good one,

​​​​​Problem still persists and not being amazing at deciphering electrical schematics is there anywhere in the service manuals that shows a distinct link between these 2 circuits of the car so I can target my trouble shooting a bit more?

Thanks in advance.
​​​

scotty305

iTrader: (2)

The factory wiring diagrams for US cars have been posted online, and the first section or two of the wiring diagram does a pretty good job of explaining how to read their wiring diagrams. https://www.rx7club.com/3rd-generati...0/#post3711033 If you spend 30 minutes with it, you should be able to find which fuses power the heater controls and the ABS module. The exact locations might not match between the US and JDM models but it's worth a try. If this were my car, I would measure the voltage at the fusebox when the heater controls are not working. It looks like most of the interior illumination lights are powered by the TAIL fuse (in the fuse box inside the cabin) and the TNS relay (in the relay box hidden near the intercooler and airbox).

c0rbin9

iTrader: (2)

I had the same thing randomly happen recently after taking a left turn at speed in my car (which is LHD). In my case, it was all the interior accessories that were dead. It was fine after restarting. Watching with interest.

Blk 93

I'm unfamilar with all 96+ JDM differences. but
something that takes very little time would be disconnecting + reconnecting connectors beside ECU from front + emissions harnesses to dash harness. They are a blue and a white connector on US versions, (not sure on JDM models, but to 1993 at least, I think they are similar). You could also do the same with connectors on ECU + connectors on ECU #2, since you handled them both. Also check for solid ground wire connections at ECU bracket, + 3 ground connections to fender, engine block + firewall, since you have multiple symptoms.
If JDM's models use a white or cream colored joint box, determine which connector of the 7, might involve those functions in a wiring diagram + check that connector is properly seated.
Next, , if all else fails, check for blown fuses. You might not fix the problem, but these steps will eliminate a lot of potential causes, with very little effort. Components you handle can unexpectedly cause other issues, often only because ground and connector contacts just aren't aren't like new anymore. If symptoms persist, I would try to borrow a 3rd ECU and/or ECU #2 if you can. I hate to say this, but sometimes "a fix" can create other problems, and what you handled would be one thing to check, but hopefully it's a connector or poor ground issue.
Let us know if there are any changes ..Good luck.

DaleClark

iTrader: (55)

First thing to always check with weird electrical issues is the wiring harness that runs over the front fender liners. If the tire rubs into the fender liner it can rub into the harness and break wires.

Jack up the front, pull BOTH WHEELS and get in there and check BOTH fender liners. Don't just peek under the car and think it looks good, get up in there fully and rule that out. May even want to pull the liner and check for damage to the harness, could have been damaged in the past and the liner replaced.

Dale