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1998 Cadillac Seville

Electrical problem
1998 Cadillac Seville V8 Front Wheel Drive Automatic 70k miles

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Cadillac Technician
gstacey

1998 Cadillac Seville sls
70k miles

Key-on engine-off, all electric works, info center displays correct info, radio, all lights, windows ac-fan, windows, etc. Works.

But with the Engine running; dashboard acts erratic, shows categories but no data-info, gas guage goes from 1/2 fuill to empty and back again over and over, headlights are on but you can't turn them off, windows don't work, radio lights are on but no sound from speakers, ac-fan speed switch works but no ac.

Car-engine starts, runs, can be driven ok except for the electrial problems listed, no ac, windows, radio, etc.

I Checked the battery, it has full proper volts with engine off and on.

Driver says that the Add coolant light has been on for 1 month but the temp guage has always been right in the middle. I checked it, it needs about 1 quart, I Just bought some premix dex-cool, haven't put it in yet.



Why does everything electrical work with key-on-engine-off but not when the engine is running?

k-o-e-o: You get data on every reading. Bell works when the key is in and the door is open and when you turn the key, gas guages work, fan works, windows work, headlight switch works, radio works, volts show as 12.0-ok.

But when the engine-is-turned-on and running all of the problems begin. Fan works but no a/c. Radio lights up but no sound from speakers, windows don't work, headlights are on but can't be turned off, info display shows up but loses all data.



Later on:

I had the owner basic-test the electrical components with key-on-engine-off for only 5 minutes, the battery-volts was showing 11.0-ok at first on the display and a few minutes later when checking it again it went down to 9.0-low volts on the display?

And then when checking the volts again on the dashboard/info display now there was no data for volts.

The battery should hardly have been affected by this low-level of testing.

All we did was checked that the bell was working when the key is in and the door is open a few times, and go through the dash-display to see that there was data for each category. Turned the radio and the fan on for a minute or 2

?

I have a battery charger and will go over there to charge the battery and get the car running again. I have a codescout 1500 scan tool and will use it. Any suggestion what to look for?



update: The battery was at 5, 6 volts, I charged the battery on a 10 amp battery charger for a lomg time and it then was up to 14.3 volts with a multi-meter.

I started up the car and the electric was acting erratic as before, after 10-15 minutes engine running everything started to work as it should, radio came on, ac was working. Windows and all lights worked, dash info showed all readings.

Voltrage read as 14.0, with AC on it went to 13.9. At first with everything working the radio light and sound would just cut out and come back on, once the ac cut off and came back on. After awhile everything was working ok.

But you could tell that the problem would be coming back.

The next day upon startting the car the dash display showed no info for the different readings just dashes.

I'm waiting now to see how they did because they had to use the car to go somewhere.

I will update this as soon as I hear how the car did on the road.

We cannot fix this ourselves, unless it's an easily accesable repair and/or parts. We'll most probably have to take it to a mechanic, but we want to try and figure out what's wrong with the car-electric, rule-out unneeded expensive mechanic quotes, such as unneeded computer repairs-parts, etc, befiore we give the car to a mechanic for an estimate-$$$

Can you help me diagnose this problem.

Thank you,
tdc
Avatar
Tdc
August 18, 2010.



Later on: I had the owner basic-test the electrical components with key-on-engine-off for only 5 minutes, the battery-volts was showing 11.0-ok at first on the display and a few minutes later when checking it again it went down to 9.0-low volts on the display?

And then when checking the volts again on the dashboard/info display now there was no data for volts.

The battery should hardly have been affected by this low-level of testing.

All we did was checked that the bell was working when the key is in and the door is open a few times, and go through the dash-display to see that there was data for each category. Turned the radio and the fan on for a minute or 2

?

I have a battery charger and will go over there to charge the battery and get the car running again. I have a codescout 1500 scan tool and will use it. Any suggestion what to look for?

Update: The battery was at 5, 6 volts, I charged the battery on a 10 amp battery charger for a lomg time and it then was up to 14.3 volts with a multi-meter.

I started up the car and the electric was acting erratic as before, after 10-15 minutes engine running everything started to work as it should, radio came on, ac was working. Windows and all lights worked, dash info showed all readings.

Voltrage read as 14.0, with AC on it went to 13.9. At first with everything working the radio light and sound would just cut out and come back on, once the ac cut off and came back on. After awhile everything was working ok.

But you could tell that the problem would be coming back.

The next day upon startting the car the dash display showed no info for the different readings just dashes.

I'm waiting now to see how they did because they had to use the car to go somewhere.

I will update this as soon as I hear how the car did on the road.

They were able to start the car and drive it to three places restart the car each time and drive home, but with the engine running there was no; radio, windows, sideview mirrors, trunk button doesn't work, dash info says battery volts ok but no # of volts or sometimes just dashes show up, no outside temperature-just dashes, the fan speed switch works but there's no AC, etc.

With the key-on engiine not running everything electrical does work.

With no key there is no clock showing, isn't that supposed to be on all of the time?

I didn't run the scan tool yet.

Tiny
Tdc
Aug 19, 2010.
I am going to do a little research, and I will get back asap. I am wondering if it is an ignition switch. I have had them in the past, cause issues. Often times it was a phantom stall that would occur at any time. In the mean time, when it is acting up, manipulate with the key, and create some disturbance around the switch. Banging on the dash and such, to see if you can induce changes.

Factoryjack
Aug 19, 2010.
Does the vehicle have ANYTHING aftermarket installed(radio, sunroof, lo-jack, alarm), if so it may need to come out, or be disconnected. With the key on, and engine off, have you run the diagnostics through the IPC, what are the codes? There are a few things to check initially. Swap out the ignition 1 and ignition 3 relays in the rear junction block, there are probably several others like it in that fuse block. It probably won't have an effect, but maybe. Check all the fuses, you can use a test light, just make sure you can trust it is working. Pay particular attention to a fuse(s) that have no power on either side, more when the vehicle is exhibiting the symptom, and report them. Does the data reset, or after it is displaying dashes and returns, it has the same values as before.
I don't feel the low coolant light is related, probably just low on coolant. The clock only displays in ACC, Key-on, and RAP, until a door is opened. And has the battery been tested, it sounds like it has a low reserve. Not that it is playing a part in the cause, it discharging can be a hinderance.

Factoryjack
Aug 19, 2010.
No aftermarket add-ons.

Does the data reset, or after it is displaying dashes and returns, it has the same values as before?

It resets.

The battery is ok now, I charged it for a very long time at 10 amps.

Why did it disharge so fast during a 10-15 minute key-on-engine-off basic elec testing, no heavy elec use at all, and then after we stopped the elec testing with key-on-engine-off the volts were down to 9.0, then overnight it went down to 5.0 on it's own?

I will run the codescout 1500 scan tool today and will get back to you with the readout.

If it was a fuse then wouldn't there be no power at all to the components it covers, or can a fuse be working erraticly causing this problem?

When I test the fuses do I take the fuse out to test across the circuit, leave the fuse in and test across the circuit, or am I also taking the fuse out and testing the fuse itself?

What do I do to perform this part of the fuse test?

" Pay particular attention to a fuse(s) that have no power on either side" I do have a test light, have necer used it before. I have never done any elec work on this car. Only on an old Plymouth 318.

I'll catch on, but I'm not sure if you want me to check the fuse socket, the fuse itself, or both.

I have a decent multi-meter for any testing that you recommend.

I'm going there now. I'll get back to you later with the test results.

They just told me that the clock shows 12: 00 when the engine is running. With key-on-engine-off the clock shows the correct time. They also said that when driving today they only had dashes for temp and bat-volts on the info display.

After driving the car for 5 minutes and the car then being turned off for 1 hour the display read 12.9 volts with key-on-engine-off, before they started the car again.

Tiny
Tdc
Aug 20, 2010.
When I test the fuses do I take the fuse out to test across the circuit, leave the fuse in and test across the circuit, or am I also taking the fuse out and testing the fuse itself?

What do I do to perform this part of the fuse test?

" Pay particular attention to a fuse(s) that have no power on either side" I do have a test light, have necer used it before. I have never done any elec work on this car. Only on an old Plymouth 318.

I'll catch on, but I'm not sure if you want me to check the fuse socket, the fuse itself, or both.

I have a decent multi-meter for any testing that you recommend.

Have you run the diagnostics through the IPC, what are the codes?

How do I run the ipc codes from the dash info buttons?

When I went to use my code scout 1500 scan tool it would only show the 1st screen with the tools patent#, and pressing the buttons would not show anything else. I took out the new batteries and reinstallled them 10 times but now the code scanner will not even turn on?

How do I run the ipc codes from the dash info buttons?

If you drive the car around for awhile the AC and other electric starts to work but after the car is off for awhile the symptoms come back again when you 1st start the car up.

I had the car running for awhile with the headlights off in the driveway and the AC and all electrical was working, every now and then the headlights would come on by themselves and then shut off even though the manual and auto hl switches were both off.

Iam trying to give you as many symtoms as I can so that you can help to direct me to the problem area.

Ididn't check the fuses or relays yet. Can you tell me how to check the fuses and/or the fuse sockets?

How do I hook up the test light or multimeter and how do I check for power at either side as you said?

Thanks,
tdc

I just had the owner of the car do a basic test. The car had 11.6 volts with no key. After starting the car there was all dashes on the info temp and volts, no power to windows or radio, etc. S

Soon thereafter the AC and all electric did start to work. Then the volts went to 14.0.

The gas guage was at first not working then it started to go om and offover and over and then just went to empty and stayed there. Even after 15 minutes of idling the engine the gas guage read empty with a full tank of gas.

Also the temp on the display changed over to all dashes towards the end of the test. But the volts was reading 14.0.

The owner says that starting 1 month ago when driving the check airbag message would shouw up and that more recently the check auto theft system message shows up when driving.

Tiny
Tdc
Aug 22, 2010.
How do I get the ipc codes from the dash buttons?

Tiny
Tdc
Aug 24, 2010.
Sorry it took me so long to get back, was having computer issues. In order to enter diagnostics, and it is limited to trouble codes/clearing trouble codes, you use the info button and the on/off button. Press and hold info up, and on/off until all the segments illuminate, and then release. The drivers info message will read ALL? Just for simplicity, we will use ALL, so press on/off again and it will change to ALL CODES. If you press on/off again, it will start displaying codes(if any) from all modules, in alphabetical order. If there are no codes in a module, it will say NO XXX CODES, and if there is no data it should say NO XXX DATA. This no data isn't always the case, if there is a module that is not communicating at all on the buss, it may not even show up. There should be upwards of 22 modules at least, I think about 24 to be exact. You can do this procedure with key on, or key on-running. The only time it won't work is if there is another scanner plugged in the DLC. It looks like your code scout is just a code reader. If that is the case, those are usually limited to emissions related codes, powertrain and maybe transmission.

If your test light is unpowered, it has a single lead that can either be grounded or powered. In checking a fuse, or if a fused circuit is powered, attach the lead to a good ground, and touch the metal tabs on the back of the fuses(each side of the amp rating), and it will light if a circuit is powered, and light on both sides if a fuse is good. Like I say, when the vehicle is acting up, check as many if not all, of the fused circuits to determine if any are missing power. From there we may be able to isolate a common power source that may be failing(relay, switch, fuse block, etc.)

Factoryjack
Aug 24, 2010.
Here are the codes: C-Current H-History

ABS: C1252-C C-1253-C C1298-C U1255-C P-ID-7208

AMP: U1255-H U1128-H U1064-H
U1016-H P-ID-836B

DDM: U1064-H U1065-H U1066-H
P-ID-6214

DIM: U1300-H U1255-H P-ID-8270

IPC: U1160-H U1064-H U1065-H
U1066-H U1088-H U1040-H U1255-H U1300-H U1301-H P-ID-807A

IPM: U1255-H U1064-H U1066-H

IRC: U1129-H U1064-H U1065-H
U1160-H U1016-H P-ID-F895

PCM: P1602-H P1611-H P1612-H P1614-H P1652-C

RIM: U1255-C 1065-H U1160-H
U1064-H U1016-H U1096-H

SDM: B1147-H B1148-H B1159-H
B1160-H B1163-H U1301-H U1096-H U1064-H U1255-H B1327-H
P-ID-8960

The problem clears up as the engine is warmed up. There are alot of fuses, which ones should I try 1st while the problem isstill happening, and should I be testing the fuses under the hood or just the fuses under the back seat?

The test light is for 110 volt, so I'll have to use the multimeter to test the fuses.

Thanks,
tdc

Tiny
Tdc
Aug 25, 2010.
Was that all the modules that displayed, or just the ones that had codes? Initially, all the codes that had a U prefix, are communications fault codes. None of them suggest a common source of the fault, which would lead me more to thinking you have a module power fault. After having them recorded, I would recommend clearing them all. Run the vehicle until it exhibits failure and then run the diagnostics again and see which codes have returned. If you are having dashes display, and having the data reset after a fault, I would look at fuses that supply power to those modules, things labeled as HVAC, AMP(AUDIO), IGN 1, IGN 3. This type of problem may occur with a loss of power supply, a poor ground that fails under load, or even a class 2 communications fault(short to ground/power, open circuit). The fact that it occurs only when running, leads me to a power supply, but I have never experienced a fault of this nature. Keep in mind that with the airbag light, theft warning, and the low coolant message, it may have some other issues that are coincidental

Factoryjack
Aug 27, 2010.
Just the 10 modules that had codes, I'll clear the codes and test again. But there were not that many that showed no codes or no data. That's far short of the 22-24 modules that you said there are. What does that mean?

The only way I was able to write down the codes for each module was to go through the list of modules 1 at a time, not the whole modules list at one time. Aren't all of the modules listed in the 1 at a at a time way too?

I'll check it all out again.

Tiny
Tdc
Aug 27, 2010.
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