: Cascading multi-module failure-BBOB?

06-19-04, 12:26 PM
I have a 99 sts with 85,400 Kms.

After a startup as I put the car into drive and started to roll all of a sudden the TC and security light came on, followed by service air bag, service suspension system and the chime started to ding. I put the car into park and shut it off. Started it back up and nothing. All lights and messages were off and had no problems since.

After checking the on-board diagnostics, I got the following codes (ALL HISTORY): I had checked the codes about 3 days before-usually do it once a month-and there were non stored in any of the modules.

Anyhow here they are:

ABS: C1298, U1016, U1056
AMP: U1301, U1064
DDM: U1066, U1064, U1065, U1016
DIM: U1255, U1065, U1016, U1066
IPM: U1064, U1016, U1066
IRC: U1229, U1064, U1065, U1160, U1016
PCM: P1602, P1064, P1611, P1612, P1613, P1614, P1615, P1626
RFA: U1305
RIM: U1064, U1160, U1065, U1016, U1096
SDM: U1301
VTD: U1016, U1064
MSM: U1305
TTM: U1300, U1255

No other codes in any other modules.

I am suspecting the class 2 serial data line (1807 PPL) is shorted to ground or intermittent connection. But where do I start if the problem comes back?

Thanks for the help,

06-19-04, 02:18 PM
I had something like that happen to me once and it was a loose batt termi I own a 96 deville don't know how different they r

06-19-04, 09:44 PM
Inspect, clean up, and tighten the battery terminals (under the rear seat), clear the codes, and start from scratch. A battery load test might be in order also.

While you have the battery negative terminal disconnected, inspect / tighten the large cable connections under the red cover at the FUSES / RELAYS box in the RF side under the hood.

06-21-04, 11:43 PM
Checking the battery cable connections and grounds is a good idea.

I doubt that you will see the problem again, honestly. It may be due to a module that was "slow" to wake up at that particular key on event for some reason....???.... If that happens then all the other modules on the serial data line freak and set codes since they didn't see the normal hierarchy of communication start up at key on... Random and rare but it happens occasionally. As Microsoft would say, restart your computer and try again....no LOL.

If the serial data link was shorting or anything it would cause WAY more problems that that. Not likely something you have to worry about.

06-22-04, 11:37 PM
I replaced the ignition switch on my 99 STS. I was having all sorts of funny things happen during startup. My ABS and Traction Control idiot lights would come on intermittently and then they would, for no reason, shut off and occaisonally come back on again.

Also, I would sometimes have a hard time starting the car. Upon running diagnostics, there was always a multitude of data-related history codes. As it turned out, this ignition switch has a bunch of contacts in it. At least one of those contacts "makes" the serial data communications circuit that communicates between all of the onboard processors.

When I pried the old ignition switch open, I saw that at least 3 of those contacts had arched enough to cause a bad contact points - kind of like worn points in an old distributor-type ignition system. So sometimes when the car was started, there would not be a good connection when the contacts pulled in. Other times it would be fine.

Upon replacement of this switch, all problems went away. It was very interesting to see some of the unexplained things the ignition switch may have caused. I haven't had any problems since though and it has been over a year since replacement.

I bought mine online from one of the GM parts sites. I can't remember which one, but it was around $50. If you have the service manuals, the changeout is pretty simple. Took me about 4 hours. I was in no hurry. You do have to remove the radio/HVAC controls. I did not drop the steering column, nor did I disconnect any of the airbag wiring, however, the service manual suggests differently. I did disconnect the battery though. You have to have the key in the tumbler as a final step to remove the assembly.

It would be interesting to find out how many other people have changed this switch out. One of the older Cadillac sites, that is no longer in existence, had some posts on this issue. There may be some on this site as well.

I don't know if this is your exact problem, but it may be something to consider.

Good Luck