Drivetrain Swap 1988 D150 (318 A500 or a518)

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Aug 17, 2023 | 06:06 AM

#11

Jfleming1997

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Quote:

Originally Posted by Moparite

The pcm doesn't switch between positive and negative, Positive is supplied from either the ignition switch or the asd relay. The pcm supplies a ground to pin 55 for lock up and 38 for od ( i go the #'s from the print you supplied). On the prints i have there is another wire that goes to the pcm to switch off/on the od. I don't have one for 89 so it may be different and i didn't see anything on the #diagram for it(it's hard to read so i may have missed it). Really need a complete wiring diagram for a 89.

I have to disagree somewhat about the switching between positive and ground, I checked both pin 55 and 38 at the 60 pin connector, with everything else (OD off switch and PTU relay) unplugged so the circuits were open. The pins switched polarity. They grounded with the key off, and supplied +12 key on. I’m not saying they just stopped suppling power with they key off, I switched the meter probe to the positive battery terminal and got a complete circuit with the pin as ground.

Aug 19, 2023 | 07:21 AM

#12

Moparite

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Not sure how you can test it without it moving 45 mph +. The pcm is not going to engage the od until that speed. Found these, Not from 89 but may help.

Aug 19, 2023 | 08:32 AM

#13