1990 Reatta wont go into Diagnostic mode

[NJ727]

So I recently purchased a 1990 Reatta, its been fairly well kept and has had a mostly trouble free life. However anytime I have tried going into Diagnostic Mode the dash only flashes, turns to normal, and keeps flashing, without ever reading any codes out. The only issue I can locate is the previous owner for some reason has rigged together the AC and Fog Lights, so that the AC kicks in when you press the fog light button (The Fog Lights are always on when the AC is on, vice versa). From what I understand from snooping around is the lack of Diagnostic mode may be caused by the oddball wiring in the Relay Box, or potentially a bad ECM/BCM.

 

Every other electronic feature seems in check, and everything on the Dash seems functional. I have included the image of what I believe is the problem

[2seater]

Is your Climate control completely functional? Do the temperature up and down buttons work as well as the fan manual control? Is the cover in place over the ALDL socket under the dash left of the steering column? If so, the first step is to unplug, clean and reconnect the ECM and BCM harness connections. Start there. I don't think that wonky wiring should cause your problem unless the wiring from the climate control panel is messed up as well.

[NJ727]

From what I can tell the Climate Control is fully functional, everything works as intended. The cover over the ALDL looks in its proper position. Ill try disconnecting and reconnecting the BCM and ECM harness connections. I believe after reviewing some of his notes he wrote down in the vehicles manual is he may have been trying to bypass the BCM. He had the original AC relay and another relay set aside in the glove compartment.

[Ronnie]

My guess is the AC got low on freon the BCM locked out the compressor. That is a safety feature to prevent damage to the compressor. He probably didn't know how to get the compressor to kick in and tried to bypass the BCM and power the compressor with the fog lights to get the compressor to run. All he had to do was disconnect the battery for a few minutes and reconnect to get the compressor to run long enough to add freon but him or his mechanic might not have know that.

 

 

[DAVES89]

I would get that wire off the headlight switch. All that power going through an almost overloaded switch that is a one year Reatta only is looking for trouble...

[NJ727]

23 hours ago, Ronnie said:

My guess is the AC got low on freon and locked out the BCM locked out the compressor. That is a safety feature to prevent damage to the compressor. He probably didn't know how to get the compressor to kick in and tried to bypass the BCM and power the compressor with the fog lights to get the compressor to run. All he had to do was disconnect the battery for a few minutes and reconnect to get the compressor to run long enough to add freon but him or his mechanic might not have know that.

This sounds like the case seeing all of the original owners drawings and ramblings in the manual relate to the AC compressor and the BCM. This weekend ill try putting the original relays back in the relay center and see if I can get the compressor to kick in. Ill keep this thread updated with some results 

[NJ727]

Apologize for late reply due to holiday, I did not end up doing the AC compressor after doing an oil change and some other monotonous maintenance, however I did find under one of the seats an old maintenance sheet from a mechanic which I believe to very important to the diagnostic problem.

 

In the papers (Which are dated 2018) he claims the AC compressor was replaced at some point, and a retrofit kit for R-134a was also installed. The units are fully functional but the original owner (now passed away) was jumping the AC system and it would then work as intended. The BCM was reading codes:

B113 - Body Temp Sensor Fault

B112 - Low Sensor Temp Sensor Fault

B333 - Loss of Inflatable Restraint System

B122 - Panel Dimming Fault

B420 - Relay Circuit Fault

B412 - Battery Volts High

B335 - No Climate Control Cluster

 

After this he claims to have tried clearing the codes "several times" and then after code clearing, the AC was fully functional. 

In a separate repair order (about 12 days after the first time these codes were retrieved and erased) he states the AC pressure was good but it had no ground from module. After a "scan" (Not from diagnostic mode as suggested in the first repair order) all the original codes as I just listed appeared once again, and he additionally retrieved two new engine codes:

47-UART Link Problem

41-No Camshaft Reference Signal

[Ronnie]

Have you checked the codes to see what codes you are getting now?

[NJ727]

Well that's my problem, the car wont go into diagnostic. The dashboard flashes like its trying but then just keeps flashing. Im pretty sure the mechanic who did it probably used a diagnostic tool (OBD1 Reader I think they are called?) 

 

Im bringing it to my mechanic in in two-three weeks give or take, I want him to replace spark plugs (which are pretty close to end of their life), transmission fluid, and do some other jobs that im not really equipped for at the moment. He specifically works on older vehicles so the AC issues (which I believe are egging on the BCM not kicking in) are in his ballpark.