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1986 Riviera electrical problems

Guest HVTType

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Guest HVTType

I recently purchased a 1986 Riviera for my daily driver after my 1990 Century rusted through and would not pass inspection. I was considering getting a Reatta, but I found the Riv on Craigslist for cheap and went for the cool, collectible electronics with a backseat and affordable glass.

The Riv runs great and the body is in excellent shape, but there are some electrical issues that I would like help with. First the basics, which are minor:

1. Radio doesn't work. Antenna and tape deck both work, so I assume that I will need to replace the receiver. If anyone would tell me where to get a proper replacement and what to look for, I would appreciate it.

2. Date and time cannot be set. The clock displays no digits and the date always says “Wednesday, January 1, 1986.” When I set them they just go back to the default after I turn off the car.

Now the real problems:

The dash panel display will randomly black out at times, sometimes for seconds, sometimes for minutes. The GCC display will sometimes black out with the dash and sometimes go to the radio screen. Often, while driving, the diagnostics screen will display: “Instrument Panel Controls Problem.” with its accompanying message.

When this happens, a relay switch starts clicking like crazy. I will hear “click-click” “click-click” which will be followed by a blackout of the dash or “beep-beep” and the diagnostic screen. The relay that clicks is the “Rap accessory 1” relay (the plug designated “H” in the relay diagram).

I checked the battery terminals and grounding connections. All are clean and tight. The fusible links in the wires appear to be good. All fuses are good. Interior lights, power seats, power windows all are functional, but I haven't tried them when the dash blacks out. When the error occurs the car drives fine with low-beam headlights.

Diagnostic screen gives the following errors: E047 (BCM to ECM data fault) and B552 (BCM memory reset.) Both of those are related to the Body Control Module. I also removed some interior panels to check out the BCM, CPS, and ECM connections (which appear to be okay, although, admittedly, I don't know much about this.) I learned that there was a GM bulletin that recalled the original Central Power Supply units, but my CPS (near the brake pedal) has no numbers on it, so I don't know if it was ever replaced. i also have an 87 buick riviera with the dash out, could having - JustAnswer

I read somewhere someone suggested tapping the CPS and notice if it has an effect, in order to check for a bad solder joint in the unit. I tried that with no effect.

Sometimes, especially in the morning, I will drive to work with no problems and no malfunctions. It always seems to occur when driving home in the evening. I would guess this is simply coincidence. This is all of the reconnaissance work that I could do before bringing the issue before this august body for consideration. Does this info narrow the problem down to the BCM? Or has someone encountered these problems before with a different culprit.

Thank you in advance for all feedback!


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Welcome to the board!

The radio issue sounds like a bad receiver as you stated. There are several parts vendors on here (look at the sticky thread "Reatta Resources") who can supply the radio receiver module. The one in your car should be identical to one in an 88/89 Reatta.

The inability to set date/time could be due to the bad radio (the clock is stored in the radio, date is stored in the CRTC), a BCM malfunction, or could be related to the intermittent IP blackout. It sounds like you have a bad central power supply (CPS), though there is an off chance there is some other module "pulling down" the voltage supplied by the CPS. Could be the instrument cluster, as I have seen similar malfunctions with a bad IPC.

I would start by getting a spare CPS and installing it (again, can get from one the parts vendors on here) to see if that solves the blackout/clock set problem. This is simple and cheap enough to do. If it doesn't fix the problem, it is good to have a spare CPS on hand anyway, they do not last forever.

If you are still having the problem after changing the CPS, then I would pull the IPC and test the car with it out. The car will run, but this will show an error on the GCC screen of course. If pulling the IPC causes the blackout problem to stop, then it needs to be replaced. If the symptoms are unchanged, I would next check the CRTC (in the console next to the radio module) by disconnecting it to see if it is causing the power dropouts. If there is still a power dropout issue at that point, then it may be the BCM.

Obviously, a replacement BCM will be needed to test this idea as the car will not work with it out of circuit. I am not sure if the 86/87 Rivi used the same BCM as the 88/89, so finding a replacement may be a bit more involved.

Hope this helps to start. I'm sure others will offer additional suggestions and ideas.


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If it makes you feel any better, owners often sell our cars (Reattas/Rivieras) because they have problems they cannot fix or have been quoted high prices to fix them.

The Teves brakes on the Reatta is a good example. Few shops know how to work on them so they quote a huge sum.......the owner has the choice of selling the car or paying their extortion.

I am impressed that you apparantly already have a service manual and have done your homework.

On our 20+ year old vehicles, electrical problems will continue to be gremlins. Sometimes it is nothing more than a bad connection, you replace the componet (like a radio) and it works, however if you now plug the old one back in place, it might also work because the connector contacts have been cleaned by the "plug-upplug" action.

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BTW that sudden blank/switch to RAP is often a maladjusted ignition switch on the steering column. The BCM can "think" the ignition is off even though the engine continues to run. When it happens try moving the key a bit toward "start" (without getting there).

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Guest Mc_Reatta

A little out of my element discussing an 86 Riviera, but will try to give some advice anyway.

Your IPC and other power issues do seem to indicate a problem with the CPS and possibly also the ignition switch as already mentioned.

I'm having a few misgivings about the nature of your symptoms however. A CPS rarely goes bad and if it did I would not expect it to be so intermittent.

A problem with the ignition switch would explain the IPC going dark and the switching of the CRT to the Radio mode as classic symptom of entering RAP power mode. This scenario should have no effect on the clock display though.

Both of these symptoms seem to be more likely due to poor connections rather than a hard electrical failure.

You mentioned that you checked the battery terminals and the fuseable links and ground point, but did you check all three common ground points under the hood.

The CPS can use both the one on the rear cylinder head under the alternator and the one on the upper radiator support behind the passenger side headlight.

Many people only see the one behind the battery by the radiator overflow tank and miss the other two. Also check for corrosion in the interior fuse and relay center as power flows thru a couple of fuses in there before going to the CPS and BCM although that is not too commonly an issue at that location.

Certainly worth checking out before replacing the CPS, IPC, BCM and ignition switch.

Clock seems to be only be dependent on the CPS and IPC, and the fact that it works while car is running but not when turned off and back on, it would seem the IPC is not the source of this problem.

Going into RAP power is possibly a BCM issue, but more likely a loss of "run" power due to faulty ignition switch.

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I've had a CPS below the dash go bad. Intially the dash would very intermitttently flicker and a relay(s) would click a few times. The problems progessivly worsened, to the point were the car had severe runnabilty/stalling issues. Tried replacing the BCM and ECM, checking ground connections etc with no sucess. I even tried a rebuilt CPS with no luck. Finally a used CPS out of another same year reatta solved the problem.

My general concern with the CPS and other electronics in cars this age is that the electolytic capacitors are failing, like those in the radio and CRT.

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Guest HVTType

Thank you for all the replies! This board is a great resource. Thanks to your advice I have an idea of how to solve the issue and more optimism that I will be able to restore, maintain, and enjoy this beautiful, classic car. :)

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  • 7 years later...

I hope this is the right location for this question.  I have a spotless garage kept '86 Riv Touring that has a strange (to me) electrical problem. After a few cranks to get it started one day the entire electrical system went dead. Absolutely nothing, like the battery was removed although I've check it and it's connections. I've also checked all fuses in the fuse box but I've heard there is also a fusible link somewhere the wiring that may have opened. Thinking this might be the problem, can someone guide me where to locate this?  Much appreciated.       woodla@wowway.com


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