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1st Time 1st Gen! Got a issue Iím trying to figure out... ECM?

Old 01-05-2019, 08:58 PM
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1st Time 1st Gen! Got a issue Iím trying to figure out... ECM?

He everyone. Just put my truck (Junior) on the road for the first time today! Bought it in July, itís a 93 LE 5 speed, JR has 131k on the clock. I have a lot of work to do, and as of now itís bone stock right now. I know the ECM voltage regulator is not working as it already has an external regulator mounted in the engine bay. I did order an alternator conversion so it will be self regulated.

I do have one issue Iím trying to track down that I believe to be ECM related. The speedo, cruise control, grid heater and tach all do not work when the truck is first started. They all eventually come to life after driving for a while (5-10) minutes. Iím thinking maybe a ground issue? Itís odd that it just sorta starts working after a while of driving. Any thoughts? Iíll try and track it down tomorrow , but I wondered if anybody may have a bit of direction for me. Thanks and Iíve already learned a lot just from poking around in the group.


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Old 01-07-2019, 04:48 AM
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I think that a bad/loose ground is likely. It sounds like the metal is expanding as it heats up and making the ground good, until it cools off again...Mark
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Old 01-07-2019, 06:30 AM
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Sweet ride.

Might want to follow Mark's idea above. As stated a million times on this forum, the grounds in our trucks are NOTORIOUS for being gunked up. I disconnect mine at minimum once a year, sometimes twice a year. That means ALL of them. The ones on the firewall, radiator support, engine block, engine block, etc.

Once the grounds are all cleaned up, and you find you're having a similar problem, look at the 3 relays on the fenderwell driver side. Believe it or not, relays do go bad. Disconnect them, make sure the ends are clean and not all gunked up, and rotate them in sequence, meaning move the same style relay to the other position and see if it fixes your problem.

Fusable links can be a real pain as well, and those are located in the same area. They can be "intermittent" as well, which why replacing them with the maxi fuses is a good idea.


Nice truck.... hope to see more of it.
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Old 01-07-2019, 01:24 PM
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Do as above....grounds are very important. But it sounds to me like your CPS is not working properly, or one of the 3(?) connection points along it's circuit is fouled up.
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Old 01-07-2019, 05:07 PM
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Thanks for the input. I was suspecting a grounding issue but figured Iíd ask for direction in case the symptoms sound familiar to anyone.
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Old 01-08-2019, 07:04 PM
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What a mess!

So I spent some time under the hood of my truck... the PO didnít do me any favors. 😒 The wireing is truly a mess. Iím gonna have to go through the whole engine bay harness wire by wire. Iím sure itíll be better off doing this in the long run.
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Old 01-08-2019, 07:20 PM
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Yes.

Your headlights should be separated onto relays. The fuseable links are junk, and can be upgraded to maxi fuses.
the heater blower motor can be separated as well, but ive never done it and have had no issues.

Most of these are dictated in the sticky, headlamps being priority as they draw their power through the ignition switch, and fuse panel above your brake pedal. Theyre known to ( the fuse panels ) melt, and catch fire....
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Old 01-09-2019, 03:53 PM
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I had a similar problem. The crank shaft sensor was not working. But the problem was the 8 volt supply from the ECM. So check the connector on the crank sensor to see it there is 8 volts DC there.
If there is 8 volts DC plug the sensor back in and connect between the signal wire and ground with a meter with the motor running. On a AC scale you should see 200 mill volts ac.
Check the air gap on the sensor 50 thousand.
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Old 01-29-2019, 09:10 PM
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DId you ever fix? I have similar issues .. been in multiple shops... Spent endless hours reading these forums and working on it myself.. There is so many speedo/no charge/fuses blow posts on here its crazy. My truck has had electrical gremlins like this for the 2 1/2 years Iíve owned it! Driving me nuts! (Iíve traced wires, poked around with meters, cleaned grounds, new alt, multi-function switch, brake light switch, rear sockets, external regulator, 100 burnt fuses).
Currently trying to figure out how to test/adjust spacing for ESS and researching CPS..

Hope I didnít scare yah and your not experiencing other electrical woes.
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Old 01-30-2019, 04:30 AM
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Originally Posted by Erbstock View Post
DId you ever fix? I have similar issues ..
No I havenít yet. Itís been too cold and snowy to mess with for now. Iím planning in the spring to go through the entire electrical system and get JR back to where he should be. Itís gonna be a big undertaking, but one that I feel is going to be worth it.
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