Hi everyone I have spent several hours on this websites search FX and on google looking for an answer but have come up empty handed so I hope someone here can help! I just picked up a 1993 RX-7 and it has several different issues however the one I am currently trying to solve is with the check engine light and wiring... I have read and reread and then read again to make sure I was grounding the TEN on the diagnostic port to ground and tried several different grounds, in addition I also tried straight from the computer 1I...............NOW For the problem when I do ground the TEN port the check engine light goes out for a sec the comes back on and stays on and does NOT flash any codes however the check engine light is always on while running.. I have read several post where people are having the same problem however they always go dead before the solution is posted. From my understanding I should not have continuity between TEN and GND while there is no jumper wire install however I DO and I also have continuity between FEN and ground which I don't think is normal. These were checked with all 4 plugs at the ECU unplugged and the battery out of the car..

To sum things up:
PROBLEM
Check engine light does not flash codes but stays on with jumper wire from TEN to GND
Check engine light is always ON while car is running

Things checked
Several different grounds
Continuity between TEN and GND with NO jumper wire installed
Continuity between FEN and GND with NO jumper wire installed
Wiring harness checked from diagnostic port to the passenger headlight no obvious damage found..

Where should I go from here????

 

Update after searching through the wiring diagram and the service manual I found that the service engine light WILL illuminate if the computer sees less than 2.5 volts at terminal 1F I have 6.5 volts at 1F so to my understanding I should NOT have a check engine light!? HEELLLLP lol

 

Ok my previous post was wrong.. I forgot that I had cleared the codes and had not restarted the car.. After restarting the car and codes coming back I am only getting .7 volts at terminal 1F .... check engine light still does NOT flash when TEN is grounded

 

have you tried unplugging the battery overnight? that will dissipate all capacitors that store ECU codes. it's an old school OBD1 system so it might just need a restart.

 

i have just spent some time figuring out how this system works in the FD.

so the TEN terminal tells the ECU to either flash codes, or if the engine is running, it runs a fixed timing and BAC setting so you can set the base idle, etc.

the CEL signal is a bit odd in the FD, the FC has an output for the CEL and an output for the diagnostic terminal, 1E and 1F. since the CEL for the FD is a US market add on, it uses pin 1F for both functions. the diagnostic port goes straight through. so you can hook an LED right up to it, and it will flash codes, it will NOT drive a normal light bulb, must be an LED.

the CEL signal splits off and goes to the E/L unit, which does some magic (seriously nobody on the planet knows) and gets it to drive a bulb in the cluster. (why didn't they use pin 1V, this DOES drive a light...)

the cluster provides power and the ECU is the ground.

 

Are you sure you have a stock ECU?

Dale

 

Thank you for the replies! I appreciate all the help I can get... So if I am understanding you correctly 1F is only responsible for sending the signal to E/L magic which then sends the signal to the check engine light...? But there is a "back up system" that operates off 1E but will only flash a L.E.D because the magic E/L does not exist? Is that correct? And if that is correct can I just use the L.E.D or do I need to add resistor like I have read in other post??

 

To be honest I do not know if it is a stock PCME..? It looks like it would be but I know very, very little about the cars history. Is there anyway to tell?

 

the wire in 1F splits, one side just goes straight to the diagnostic box. the other leg goes to the E/L unit, and then the CEL bulb.

since there is one signal, its the same for both wires. since i have an FC, i tried hooking the CEL up to 1F and it doesn't work, but it works fine with an LED, so you can use an LED in the diagnostic box.

you should pop off the kick panel, if theres a power FC in there, then that would explain why the CEL doesn't work, the PFC is wired for a JDM car, so there is no E/L unit, and it uses 1V for the CEL...