Mechanics

KEEP HAVEING TO REPLACE IGNITION MODULE

1993 GMC C1500

Electrical problem
1993 GMC C1500 6 cyl Two Wheel Drive Automatic 156000 miles

I'm stuck. I have replaced the ignition module in this truck many times. Only will run now about 1 hr before it burns out. I have replaced fuses, computer, dist. Cap & rotor where to go from here? Is it a short? Is there something that regulates the voltage to the ignition module?
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Allenb2261
August 12, 2010.




Any codes? Service engine light on? Your engine size will help. Cant look up specifics without engine.
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Merlin2021
Aug 12, 2010.
4.3 liter v6

Code is 042
Faulty ignition module or faulty wiring

Each time I have replaced Ignition module code goes away. But like I say after a short time running the truck the module will burn out again and the code comes back.

I have checked the wiring as far as I can. Everything appears correct.

Tiny
Allenb2261
Aug 12, 2010.
Code 42 indicates ECM has seen an open or short to ground in High Energy Ignition Electronic Spark Timing (HEI EST) system or by-pass circuits. 1. This test confirms Code 42 and determines if fault is a hard failure or intermittent condition. 2. This tests for a normal EST ground path through ignition module. If circuit No. 423 is shorted to ground, reading will be less than 500 ohms. 3. As test light voltage touches circuit No. 424, module should switch. This causes ohmmeter to "over-range" with meter in 100-200 ohm range. A higher ohm range will indicate over 5000 ohms. This test assures module switched. 4. If module did not switch, this step tests for a short in circuit No. 423, an open in circuit No. 424 and a faulty ignition module connection or module. 5. This step confirms Code 42 is a faulty ECM and not an intermittent problem in circuits No. 423 and 424. NOTE: Test numbers refer to test numbers on diagnostic chart.


http://www.2carpros.com/forum/automotive_pictures/62217_code_42_1.jpg


Check purple/white and tan/black wires from the module right to the PCM, unplug both connectors pcm and module, check wires with an OHM meter, you should have a zero reading on each wire. if it's OL or high reading, the wire is damaged, trace it and fix it. Also these trucks had an updated mem cal for the ecm(pcm). does yours have it?

Merlin2021
Aug 13, 2010.

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