2nd gear starts with abs/traction control disabled?

[Dusty95]

First off I want to say hello, I just purchased my first cadillac a week ago. It's a '95 STS. I hope to rip this car apart piece by piece over the years and learn everything I can about it, so I can master the electronics within' this beauty.

Ok, for the car's first problem. I brought it home with no heat and no info from the mpg/trip counter and the abs light staying on only after the car was shut off...draining the battery. The fix here was easy, the harness shorted out on the abs/traction control module and was bringing the entire UR Data line down, allowing no communication with my shop's scanner. Upon unplugging the module and cutting away the burnt harness, data was back online. I again have temperature control and the mpg/trip function works again also.

I decided to take the car for a spin to see how badly the car really needs abs and traction control (module is unplugged still at this point) My information center is displaying Traction Disabled, but there are no abs lights on.

The only problem I see is that the car has 2nd gear starts. You cannot even manually put the car in first gear. My question to you guys out there is this a problem that is related to having the traction control offline? Basically a traction control failsafe? I could live without abs and traction control, but if the car is always going to skip first gear I'll have to buy a new harness, connector and module.

Thanks for your time

[BodybyFisher]

With the traction control OFF the tranny is defaulted to a second gear start. This is done to protect the axles and transaxle from an over torque condition. When you are in snow for instance, the PCM ABS system will pulse the brakes and even drop cylinders to prevent wheel spin and overheated brakes.

[Cadillac Jim]

The Northstar system is a set of modules that interact through the network and support OBD II. The ones you have already interacted with are

• IPM, the intstrument panel module, which drives the OBD II interface and the displays on the instrument panel including the odometer and trip odometer, and driver messages such as "Traction disabled." You can get a list of all messages, not just the most important one, by pressing "Reset Info" on the driver information console (DIC), the set of buttons that control the displays.
• PCM, the platform control module, which controls the spark, fuel injection, transmission, and engine cooling fans.
• TCS, traction control system.
• PZM, platform zone module, which handles the suspension and other things.

In a minimally configured (taxi or such) there will be about 10 modules. In a loaded STS or Deville, there will be over 20. They all interact and many are programmed according to the vehicle configuration. An example is the fact that the PCM won't use low gear unless the traction control is enabled because it can't control the transmission torque.

The best way to fix a Northstar system is to bring all the systems and modules up and have the system generate no codes, or no codes of significant codes A persistent lumbar sensor error in the memory seat module -- MSM -- is an example of one you can ignore. Perhaps you can fix a Northstar system by disabling some modules for optional equipment and configuring the others so that the option is not expected to be installed; you can remove a factory phone this way.

Your question apparently is: what is the minimum set of modules that is necessary for a Northstar system to run OK with no messages and no Check Engine light -- and the answer is all of them, except some optional accessories.

[Dusty95]

Thanks for the good info guys! I suppose I'll have to invest in a new abs module and get a new piece of harness that was fried. Perhaps I'll stick a WTB ad up on the site. Can't wait to see what this car feels like with 1st gear, feels fast enough using only 2nd and up.

[BodybyFisher]

Here is some interesting information:

Antilock Brake System (ABS)

When wheel slip is noted during a brake application, the ABS will enter antilock mode. During antilock braking, hydraulic pressure in the individual wheel circuits is controlled to prevent any wheel from slipping. A separate hydraulic line and specific solenoid valves are provided for each wheel. The ABS can decrease, hold, or increase hydraulic pressure to each wheel brake. However, it cannot increase hydraulic pressure above the amount which is transmitted by the master cylinder during braking.

During antilock braking, a series of rapid pulsations will be felt in the brake pedal. These pulsations are caused by the rapid changes in position of the individual solenoid valves as they respond to their desired wheel speed. This pedal pulsation is present during antilock braking and will stop when normal braking is resumed or when the vehicle comes to a stop. A ticking or popping noise may also be heard as the solenoid valves rapidly cycle. During antilock braking on dry pavement, the tires may make intermittent chirping noises as they approach slipping. These noises and pedal pulsations should be considered normal during antilock operation.

The vehicle may be stopped by applying normal force to the brake pedal. Brake pedal operation during normal braking should be no different than previous systems. Maintaining a constant force on the pedal will provide the shortest stopping distance while maintaining vehicle stability.

Traction Control System (TCS)

Traction control will not have any effect on the operation of the vehicle until the control module detects one or both of the front wheels rotating faster than the rear wheels. At this time, the electronic brake and traction control module (EBTCM) will request the powertrain control module (PCM) to reduce the amount of torque applied to the drive wheels. The PCM does this by retarding timing and selectively turning off fuel injectors (up to a maximum of 5). The EBTCM will apply the front brakes, thus reducing torque to the front wheels. Once the front wheels begin to rotate at the same speed as the rear wheels, the system will return full control to the driver. During Traction Control mode, if the brake is applied to only one front wheel, most of the torque from the engine will be directed to the other front wheel which will improve the traction of the vehicle.

The braking is accomplished by closing the TCS master cylinder isolating valves, this isolates the master cylinder from the rest of the system. The TCS prime valves open to allow the pump to get brake fluid to build pressure for braking. The drive wheel circuit solenoids are energized as needed to allow for pressure hold, pressure increase, or pressure decrease.

The TCS may be deactivated by the driver, if desired. In order to deactivate the TCS with the engine running, depress the traction control disable switch. The system will remain deactivated until the ignition switch is cycled, or the switch is pressed again.

Service Precautions

Observe the following general precautions during any ABS/TCS/ICCS service. Failure to adhere to these precautions may result in ABS/TCS/ICCS system damage.

• Carefully note the routing of the ABS/TCS/ICCS wiring and wiring components during removal. The ABS/TCS/ICCS components are extremely sensitive to EMI (electromagnetic interference). Proper mounting is critical during component service.
• Do not use a quick charger for engine starting or for battery charging with the battery still connected. Brake failure or ABS/TCS component damage may result.
• Unplug the EBTCM harness connector before performing electric welding procedures.
• Disconnect the battery with the ignition OFF.
• Disconnect the EBTCM connector with the ignition OFF.
• Do not attempt to repair the BPMV or any other non serviceable ABS/TCS/ICCS components where noted in this section. Many ABS/TCS/ICCS components are serviceable by component replacement only.
• Do not hang the suspension components from the wheel speed sensor cables. The cables may be damaged.
• Do not subject the EBTCM to temperatures of more than 85°C (184°F).
• Do not use petroleum based fluids in the master cylinder. Do not use any containers previously used for petroleum based fluids. Petroleum causes swelling and distortion of the rubber components in the hydraulic brake system, resulting in water entering the system and lowering the fluid boiling point.
• Inspect the ABS/TCS/ICCS system after service using a scan tool.

The Traction Control (TRAC) OFF switch is in the glove box. This switch allows the driver to select a second gear start. Select a second gear start if the vehicle is stuck in snow, in sand, or on ice.

The TRAC OFF switch is a momentary contact switch. Depressing the switch creates a ground path for the Instrument Panel Integration Module (IPM) ignition voltage input. When the IPM senses this voltage drop, the module turns OFF the traction control. The IPM sends a serial data message to the Electronic Brake and Traction Control Module (EBTCM). The EBTCM sends a serial data message to the PCM. Upon receiving this signal the PCM commands a second gear start for that ignition cycle.

Following this (and every) ignition cycle, Traction Control returns to an active state. The transmission again achieves a first gear start.

The Driver Information Center (DIC) Information button is on the instrument panel. Pressing the Information button displays the Traction Control state. When the DIC displays TRACTION READY, the vehicle achieves a first gear start. When the DIC displays TRACTION OFF, the vehicle achieves a second gear start. The DIC will not update the traction status display when the TRAC OFF switch is pushed and a scan tool is installed. After removing the scan tool the ignition must be cycled in order to update the DIC.

[JimD]

I would repair or replace the harness before I bought a module.

[Dusty95]

Hey, thanks for the info, I'm learning a lot here. I almost got excited there thinking maybe the traction control was only switched off and I could turn it back on, then I read on further...it should have came back on next ignition cycle. So this pushes us back to Plan A: reinstall a new abs module/harness.

Jim- I would do the same, but the module was physically melted where the connector plugs in to it.

[BodybyFisher]

If the traction control button is OFF, the traction control remains off.. check it

[WarrenJ]

Two quick points:

Dusty95's vehicle is almost certainly OBDI, and I wouldn't expect it to have a traction control button in the glove box.

Regards,

Warren

[BodybyFisher]

Two quick points:

Dusty95's vehicle is almost certainly OBDI, and I wouldn't expect it to have a traction control button in the glove box.

Regards,

Warren

Good point, I need to buy a 94/95 manual...

[JimD]

Good point, I need to buy a 94/95 manual...

Then you will need inventory tags...

[BodybyFisher]

Good point, I need to buy a 94/95 manual...

Then you will need inventory tags...

[Dusty95]

Oh, I thought "Following this (and every) ignition cycle, Traction Control returns to an active state. The transmission again achieves a first gear start." meant that it would automatically reactivate traction control without hitting the button again, I guess I read that wrong.

Yeah I'm pretty sure this is a OBD1 car, I have no MAF (which I don't mind ).

So I probably don't even have that button hey? That sucks. I'll check it when I go back to the shop Monday.

[Cadillac Jim]

You do have a MAF because it's an integral part of the fuel injection design. What you seemed to be referring to in your first post was the MAP, an air pressure sensor on the intake manifold under the beauty cover. You probably do have a way to disable the traction control. I'm surprised that you don't have a button in the glove box frame.

[BodybyFisher]

Oh, I thought "Following this (and every) ignition cycle, Traction Control returns to an active state. The transmission again achieves a first gear start." meant that it would automatically reactivate traction control without hitting the button again, I guess I read that wrong.

Yeah I'm pretty sure this is a OBD1 car, I have no MAF (which I don't mind ).

So I probably don't even have that button hey? That sucks. I'll check it when I go back to the shop Monday.

I called up your owner's manual last night and did not see a switch to turn off the traction control like I have in my 96.. Plus Warren had a 95 and I am sure he is accurate with his statement above..

[Dusty95]

You do have a MAF because it's an integral part of the fuel injection design. What you seemed to be referring to in your first post was the MAP, an air pressure sensor on the intake manifold under the beauty cover. You probably do have a way to disable the traction control. I'm surprised that you don't have a button in the glove box frame.

Nope, I do not have a MAF (Mass Air Flow) sensor. That I can say with 100% certainty. I had the air intake off while I was inspecting the abs module/harness.

[WarrenJ]

Then you will need inventory tags...

That would be funny except for two things:

Mike, from time to time, dredges up articles, old posts and errata that even the best Internet "Search Specialist" couldn't possibly produce.

And, he has photos of everything he has ever owned, repaired, reconditioned, parted-out, disassembled, sold, enjoyed or coveted.

I suspect he is no stranger to Inventory Tags.

Regards,

Warren

[BodybyFisher]

Warren, you are giving me more credit than my 1 terabyte of hard drive storage deserve. I'm just a packrat. With a laptop and desktop now, its getting a little out of control, I need to do some house keeping... Thx

[WarrenJ]

Warren, you are giving me more credit than my 1 terabyte of hard drive storage deserve. I'm just a packrat. With a laptop and desktop now, its getting a little out of control, I need to do some house keeping... Thx

Such modesty!

[WarrenJ]

Warren, you are giving me more credit than my 1 terabyte . . . .

Do you really need to hear more?

I rest my case.

Regards,

Warren

[sonjaab]

If indeed your ABS module is shot...........Before you spend that

almost $1000 for a new one at the dealer check out the ABS

rebuilders advertising on Flea=Bay. They rebuild and warranty

their work. The cost is around $175 !

Good reports on several Caddy (and GM truck sites) from folks

who have done this..........................geo

[BodybyFisher]

Warren, you are giving me more credit than my 1 terabyte . . . .

Do you really need to hear more?

I rest my case.

Regards,

Warren

Hey are you busting my chops... Leave my OCD alone...

[WarrenJ]

Warren, you are giving me more credit than my 1 terabyte . . . .

Do you really need to hear more?

I rest my case.

Regards,

Warren

Hey are you busting my chops... Leave my OCD alone...

O.C.D. = Obsessiive Compulsive Disk-drive-space-I-can't-get-enough-of ....

It fits.

[BodybyFisher]

[Cadillac Jim]

Dusty95 -- the MAF isn't under the intake manifold. It's built into the throttle body in front of the butterfly. The sensor on the intake manifold is the MAP, an air pressure sensor. I'll post a picture from the FSM tonight if you don't understand what I mean.