: 1990 Seville-Message DTC R026 / RO33

10-27-10, 05:33 PM
I've got an issue with my Cadillac.

When I'm driving, and when I turn on the heater in "Warmer" position, it sometimes cuts itself off and blows cold air, just like if it was in the highest "Cold" position.
At this moment, there's anything appearing on the board computer screen, only this:

On the dashboard, the SES light is turned on:

The only way to cut off the blower fan and the digital message displaying system is to cut the ignition. Just before the whole system shuts down, a new message appears on the screen, and lasts only two seconds:

After turning on again the ignition, the computer says that the whole system is OK. However, I took a look to the trouble codes. Those are(in the right order of appearance):
-E052.............................................. ... PCM Memory Reset
-B552....................................... BCM Memory Reset Indicator
-R026.................................... Driver Initiator Circuit Open
-R033.......................... Steering Diode Shorted in Arming Sensor

Why does this ECM? code stands here? And what are precisely the problems that my car encounters?

Thank you a lot for your help!

the recluse
10-30-10, 12:35 AM
Have the alternator and battery tested.

A steering diode "steers" current from one voltage supply to another. In a charging system, when voltage supply drops below 12 volts from the alternator, the diode "steers" the voltage back to the battery. If teh alternator starts working again, it will switch back. With the voltage flip-flopping your PCM and BCM will get reset often. Your BCM controls, among other things, the air mixture door in your A/C.

The arming sensor is what is throwing me off though. The arming sensor that I'm thinking about is for the air bag deployment, but your not throwing any SIR codes.

Anyway, HTH...

11-01-10, 11:18 AM
Ok, thank you a lot!

Well, I think too that the problem comes from the air bag. I'll try to do something about this problem...And I must fill my A/C with some new gas(Before, it was an R12 one, but now I can use a "Deepcool" gas). Maybe the system shuts down because of this?

My whole airbag stuff has been already cut off from my system on my 1991 Firebird by her previous owner, and I want to do the same thing on my Seville.
Can I do this? I attempted to remove it, but the system shuts down when I try to turn on the ignition.

the recluse
11-01-10, 08:56 PM
I attempted to remove it, but the system shuts down when I try to turn on the ignition......Can I do this?

No. :nono: A 1991 Firebird ECM is not linked in unison with some 9 other computers as is in your Seville, no wonder your having issues...plug everything back in. If you did, make sure all connections are tight. The car will only set an R026 code if there is an improper connection of the two-way SIR connector at the base of the steering column or two-way yellow connector at the top of the steering column, or an open SIR coil assembly or an open driver inflator module. If the car is not running right, disconnect the battery for about 3-5 minutes and reinstall. This should clear the codes. See if the problem persists...

The A/C issue might be from a lack of freon or a bad BCM, you'll never fully know without a set of gauges. Dumping gas in the system is no good unless it is properly charged to be within spec.

12-21-10, 12:38 PM
OK, thank you a lot for your answer. It helped me a little.

I cleared all the error codes, from the SIR to the BCM and ECM. I filmed it, and here's the video.


Well, it works better now.