Question about 1990 GMC Sierra
The first thing you should do is to locate the oil pressure switch/sending unit.
It's a single wire terminal with plastic connect sensor from the engine block.
This oil switch is about $30.
This switch serves two functions.
1) provide oil pressure reading
2) disable the fuel pump relay in event of oil pressure loss.
When this switch is failing to provide the correct pressure to the ECU. The wiring harness can overheat and eventually create a short.
ECM B blow is because the harness is grounding/shorting.
DO NOT drive the truck until you change the oil pressure switch.
After you change the switch,you should spend sometime to inspect the wiring between the fuel pump relay,ECU and fuel pump.
Please post up day on the comment window/page.
I will follow up on it later.
Posted on Aug 03, 2009
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Posted on Jan 02, 2017
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