CUSTOM CRUISE III TROUBLE SHOOTING/DIAGNOSIS

VEHICLES AFFECTED: All Models

CONDITION INOPERATIVE SYSTEN

CAUSE CORRECTION

No power to module terminals Check fuse, brake and clutch 'G' and 'A'. switches, turn signal handle, pinched wires in steering column.

Open 'ground' at module Repair ground circuit, (run terminal 'J', servo terminal new ground if necessary). 'C', or VSS ground.

Open SPS circuit (module-servo Repair leads and/or replace leads F-B, H-D or SPS coil in servo. servo).

Vac release valve circuit Adjust or replace vacuum open to atmosphere. release valve, check hoses, or repair circuit.

No high and low voltage Check for open leads or bad signal at module speed sender buffer amplifier or speedometer. terminal 'D'. Check ground and B+ input.

No 12 volt signal at module Check for open lead or connector 'set/coast' terminal 'L'. or bad turn signal handle. Check for terminal in proper cavity.

No vacuum at small hose to Check for plugged, pinched, servo. disconnected vac hoses, incorrectly positioned 3 way check valve, restricted engine vacuum fitting.

Cocked servo position rod Replace servo. and spring.

Leaky servo and/or inoperative Replace servo. valves.

Disconnected servo linkage. Reconnect.

Inoperative module. Replace module.

CONDITION VEHICLE SURGES

CAUSE CORRECTION

Excess slack in servo linkage. Adjust.

Dry speedometer cable. Lubricate.

Spikes on B+ lines. Find cause and repair.

Turn signal or other electrical Reposition electrical leads device interference. away from cruise or VSS buffer leads. Check for poor ground at module, servo, or VSS buffer.

Restricted (kinked or leaking) Inspect hoses and reposition vacuum supply hose to as required. accumulator or servo.

Crossed vac and vent electrical Rewire. leads between module and servo.

Binding servo Bowdin cable. Replace.

Torque converter clutch Normal (not a cruise problem). cutting in and out.

Intermittent ground. Check for poor ground at servo, module, VSS buffer. (Generally this is a common ground at the I.P. or servo.)

Servo valves sticking. Replace servo.

Inoperative module Replace module.

CONDITION CRUISE SET SPEED HIGH OR LOW

CAUSE CONDITION

Excess slack in servo linkage. Adjust.

Incorrect module part number Make correction. usage.

Inoperative module. Replace.

CONDITION NO RESUME FUNCTION

CAUSE CORRECTION

Incorrect operator technique. Advise operator. (If R/A held down for more than 1 second, system reverts to accel mode. Speed at time of release is new cruise speed.)

Open connection at terminal Repair. 'A' of module or terminal in wrong cavity.

CONDITION NO 'TAP DOWN' FUNCTION --------- CAUSE CONDITION ----- ---------- Incorrect operator technique. Advise operator. (Tap down held down in excess of .4 second.)

Incorrect module usage. Make correction.

CONDITION VEHICLE CRUISES OR RESUMES BEYOND SET SPEED

CAUSE CONDITION

Crossed vac and vent wires. Rewire.

Inoperative turn signal mode Replace. control switch.

Sticking valves in servo. Replace servo.

Binding throttle linkage. Make correction.

Inoperative module. Replace module.

Incorrect module usage. Make correction.

Inoperative speed sensor buffer. Replace buffer.

CONDITION CRUISE DROPS OUT WHILE TAPPING DOWN

CAUSE CORRECTION

Inoperative module. Replace module.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.