WHEEL SENSORS...

[voicepro]

Well, drat! Few weeks ago my 98 DeVille starts giving me a dash display that says "Service Stability System." It's interconnected to the anti-lock braking and traction control, so

those icons showed up even when I cancelled the SVS STAB SYS display. First thing I did was to have the tires rebalanced and rotated, even though it was a little early for rotation on this set of tires. Checked the brake pads while the tires were off, and all appears good in that regard. But that same code kept showing up intermittently. So today I went to my pal's garage and we pulled every wheel, and unplugged and replugged the sensors. Checked tire inflation while we had them off, too. Then I cleared all the codes and headed home...and

after a few miles....there's that doggoned SVS STAB SYS display again. Really has me scratching my head....not a good thing, since I'm bald and I can draw blood when I'm really

confused about something. Help me out here...if it's a faulty sensor, how the heck do you figure out which one? And does anyone know whether the sensors are part of the wheel

assembly on a '98 DeVille or are bolt-ons? How can you tell...pull the wheel itself and not just the tires? Along with this I was getting an occasional Service Engine Light, but it

doesn't appear regularly, so I discounted it as an anomaly. Oil still has three grand to go before a change is indicated, and I'm running top-quality synthetic. Giving some thought

to a new set of plugs, but that has nothing to do with that pesky SVS STAB SYS indication. At the moment, I haven't a clue. Sigh.....

[99EldoETC]

Hi, Does the Message also give you a number? If you see CadillacJim on his profile there is a link to a webpage he prepared with code meanings.

I have a 99 Eldo, no clue if they are similar or disimilar in this regard but here is what the Owners Manual says:

SERV STABILITY SYS - 54 :

If you ever see theSERV STABILITY SYS message, it means there may be a problem with your stability enhancement system.

If you see this message, try to reset the system (stop; turn off the engine; then start the engine again).

If the SERV STABILITY SYS message still comes on, it means there is a problem.

You should see your dealer for service.
Reduce your speed and drive accordingly.

If you find more code meanings please post them here.

edited to add link

[Texas Jim]

Please pull the codes and post them here...

Hopefully there will be a good clue in the codes to point to the problem.

[99EldoETC]

@Texas Jim Jinx! lol

[Cadillac Jim]

The OBD II codes will tell exactly what turned on the SVC STAB SYS message. That will point to a specific connector, etc.

[voicepro]

Okay, here are the codes my DeVille is showing: PCM PO741 CURRENT...ACM B1340 HIST...TCS C1228 HIST...MMM B2148 HIST

The MMM is the mirror memory module, and I ignore it. Not sure what the ACM is...but PCM and TCS both deal with the power train and

or traction control. So what's causing this ongoing SVC STAB SYS notice? I've done all I know to do at this point, and I'm reluctant to turn

it over to the shop for what may be something I can deal with myself.

[Texas Jim]

C1228 - Right rear excessive wheel speed variation.

I would venture a guess that the sensor is bad... assuming you have checked it and unplugged it plugged it back in 3 or 4 times.

I "THINK" it can be replaced without replacing the hub... Hopefully someone will correct me if I am wrong.

[Cadillac Jim]

P0741 TCC System Stuck Off CURRENT
B1340 Air Mix Door One Movement Fault
C1228 Right Rear Excessive Wheel Speed Variation
B2148 Right Front Mirror Vertical Position Sensor Circuit Low

You might look at the vacuum servo on the air mix door on the passenger side.

You realize that the P0741 may mean that you need a torque converter?

[voicepro]

Many thanks, Jim. I'll check all this. RE: PO741 and possibly needing a torque converter, I can't detect any problems

when driving the car. Shifts all seem normal, and I'm getting very good mileage. What should I do to explore futher

into this item? My guess is that replacing the torque converter is rather pricey...

[voicepro]

Noticed another 98 DeVille owner with a similar PO741 display, and you advised checking the brake pedal switch setting. As it happens, my

cruise control doesn't engage presently, and you said that's one symptom of the brake switch being maladjusted. Think I'll check that first

before hitting the panic button for a torque converter replacement. Many thanks for all your posts. Very helpful.

[Cadillac Jim]

The P0741 means that the Torque Converter Clutch (TCC) isn't engaging. The most common causes are a bad solenoid and a bad TCC clutch. A bad solenoid will usually throw a P0740 or P0743 code showing an electrical problem has been detected, but it can just be sticking and cause a P0741.

You can drive with a P0741 without problems. The TCC engages when you are over 45 mph at light throttle and you won't feel it engage. But when the TCC is engaged, the torque converter will not slip more than a few RPM. It gives you about 1 MPG better fuel economy on the highway and keeps the transmission cooler.

A lot of people drive for years with the P9741 without problems. But we had one long-time Caddyino contributor recently that had a bad TCC clutch give off debris that caused him to need a complete rebuild, not just a torque converter.

The GM manuals tell you not to bother servicing a 4T80E, but their end-of-life horizon is 100,000 miles, which is early middle age for a modern Cadillac. You are well advised to have your transmission serviced every 60,000 miles or so.