INCORRECT WIRING COLOURS AND TERMINAL ID. ON PG. 6E3-46
VEHICLES AFFECTED: 1986 Models Equipped With 2.5L TBI Engines and Canadian Certified Emission Systems (Open Loop)
The distributor connector wiring colours shown on page 6E3-46 Canadian Service Manual Supplement are incorrect. The correct identification is as follows:
Terminal B (CKT 424) should be Tan/Black (shows as white).
Terminal D (CKT 423) should be White (shows as Tan/Black).
The Black connector terminal identification is also wrong. The correct identification is as follows:
CKT 423 (EST) should end at terminal 19 (shows as 10).
CKT 424 (BYPASS) should end at terminal 10 (shows as 19).
CODE 42, ELECTRONIC SPARK TIMING (EST)
Code 42 means the ECM has seen an open or short to ground in the EST or bypass circuits.
1. Confirms Code 42 and that the fault causing the code is present.
2. Checks for a normal EST ground path through the ignition module. An EST CKT 423 shorted to ground will also read less than 500 ohms; however, this will be checked later.
3. As the test light voltage touches CKT 424, the module should switch causing the ohmmeter to "overrange" if the meter is in the 1000-2000 ohms position.
Selecting the 10-20,000 ohms position will indicate above 5000 ohms. The important thing is that the module "switched".
4. The module did not switch and this step checks for
o EST CKT 423 shorted to ground. o Bypass CKT 424 open. o Faulty ignition module connection or module.
5. Confirms that Code 42 is a faulty ECM and not an intermittent in CKTS 423 or 424.
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.
