Auto Service World
Feature   March 1, 2003   by Rich Diegle

Double Trouble

Buick, Oldsmobile and Pontiac ABS and TCS Trouble Lights On

On any given day, you might get a customer who comes to your shop complaining that the amber antilock brake (ABS) warning and (if equipped) amber traction control system (TCS) warning lights are on. Other symptoms may include:

The antilock brake and the traction control systems are inoperative.

The Electronic Brake Traction Control Module (EBTCM) Diagnostic Trouble Code (DTC) 61 is set.

The red brake warning light is off.


What’s the Cause, Rich?

Hey, I’m so glad you asked that. No matter how technologically advanced today’s automotive electrical systems have become, they still fall victim to the same age-old adversaries – moisture, vibration and corrosion. In this case, moisture trapped in a wire harness comes in contact with the ground splice for the Pressure Modulator Valve (PMV) motor and is wicked down a connector to the 4-way brake PMV connector. Sufficient moisture in the connector will interfere with the “pump run signal,” causing the DTC 61 to be set. By the way, this condition DOES NOT damage the EBTCM.

Models Affected

The following models that were built prior to June 1, 1995 are included:

Buick LeSabre, Park Avenue

Oldsmobile Ninety Eight, Eighty Eight

Pontiac Bonneville

Easy Repairs

The repairs are fairly routine once the problem has been identified – get rid of the moisture, seal the splice connector and stop the problem from happening again. The following repair procedure should satisfy all three tasks:

1. Remove the air cleaner and the windshield washer reservoir. For 3.8 liter super-charged engines, if equipped, remove the auto level control air compressor.

2. Remove the flexible conduit covering the main harness six inches in both directions from the point where the wires break out and go to the PMV motor connector C2 (see Figure 1).

3. Locate splice S129 (see Figure 2) and remove the tape covering it. It is located about 2 inches forward from the point where the wires break out of the wiring harness going to the connector C2.

4. Open connector C2.


5. Using an air nozzle, blow compressed air down terminal E (see Figure 3) on the harness side of connector C2 until no fluid can be seen being expelled from the wire at S129. This could take several minutes.

6. Thoroughly dry splice S129 and the wires 2 inches in both directions and clean the wires with an alcohol wipe. Allow the wires to completely dry after cleaning.

7. Cut a 2″ x 2″ piece of electrical moisture sealant tape. Apply the moisture sealant patch to the splice by folding it over the wires. Make sure that there is at least a 1/8-inch gap between any parallel wires to ensure that the patch can seal between the wires (see Figure 4). Press the patch together with your fingers or duck bill pliers, making sure that the wires are completely sealed.

8. Return the harness to its original condition making sure that the conduit seam in the area of the splice is on the bottom of the harness or slit the bottom of the conduit and make sure that any tape used to secure the conduit will allow any trapped fluids to drain.

9. Using a brush such as an acid brush, thoroughly coat both the male and female terminals of connector C2 with your favorite electrical connector grease.

10. Reconnect connector C2 and reassemble the washer fluid reservoir, air cleaner and, if necessary, the auto level control air compressor.

That’s the extent of the repair. Not only is the problem fixed, you’ve also effectively prevented the problem from reoccurring.

Bonus Tip

Here is a quick-tip related to a problem that will also illuminate the ABS and TCS trouble lights. The same group of vehicles from the previous tip are involved.

The ABS and TCS lights can come on and a DTC 45 will be set if the ABS relay is not operating properly due to low system voltage. To repair this problem, replace the original ABS main relay with a new relay designed to operate during periods of low system voltage. Make sure you check for moisture, corroded or broken terminals. After replacing the relay, clear the code and perform a functional test.

ALLDATA is a registered trademark of ALLDATA LLC

Written by ALLDATA Technical Editor, Rich Diegle. Rich is an Advanced Engine Performance Certified, ASE Master Technician with an AA Degree in automotive technology and 22 years of dealership and independent shop experience.

Alldata Quick Tip


If your customer complains of neck-snapping shifts from their 1994 ES 300 automatic transmission, the following adjustment will improve the 1-2, 2-3, & 3-4 shifting quality.

1. Test-drive to confirm the customer’s shift complaint. Now that your neck’s sore…

2. Check the throttle cable adjustment.

Hold the accelerator pedal in the fully depressed position and then loosen the cable-adjusting nuts.

Adjust the cable to obtain .04 inch (1mm) between the end of boot and the cable stopper, then tighten the adjusting nut.

Fully depress the accelerator pedal and recheck the adjustment.

3. Adjust the accumulator backpressure.

Drain the transmission fluid.

Remove the oil pan and gasket.

Set the accumulator backpressure to the lowest position.

NOTE: Depress the accumulator backpressure plug slightly inward with a screwdriver and turn the plug to the full right position. The plug will then be set to the most protruded position.

4. Install the oil pan with a new gasket and refill the transmission with ATF.

5. Reconfirm the shift quality after a 30 minute test drive with the pattern select switch at the “NORMAL” position.

The vehicle should be driven under typical operating conditions for a full 30 minutes because the ECU must re-learn the updated logic.

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