Yesterday, I drove the truck about 10 miles. When I went to go start it up again it moved 5 feet then shut off. I got a water In fuel light, so I drained the filter and primed the system. When to start it and it wouldn’t even try to crank. Found my ecm fuse popped so I replaced it and it fired right up and I drove it home. About 30 minutes later I go to leave and truck is dead. New batteries installed it fires up but I get the “battery not charging” and “water in fuel” lights on the DIC. Put a new reman alternator on it and same issue. Took the alternator to get bench tested and it passed, I still swapped it with a new (not reman) alternator and tested it before leaving and it passed. Installed it and same issue.
parts I have thrown at the truck so far:
2 new batteries
New alternator
Water fuel sensor
Alternator plug
Replaced alt to battery cable with a 4 gauge wire
I have also opened the harnesses in the wheel well and chased the alternator plug wires
still getting the lights, batteries aren’t charging from the alternator. What else could it be? Please help!!
Yesterday, I drove the truck about 10 miles. When I went to go start it up again it moved 5 feet then shut off. I got a water In fuel light, so I drained the filter and primed the system. When to start it and it wouldn’t even try to crank. Found my ecm fuse popped so I replaced it and it fired right up and I drove it home. About 30 minutes later I go to leave and truck is dead. New batteries installed it fires up but I get the “battery not charging” and “water in fuel” lights on the DIC. Put a new reman alternator on it and same issue. Took the alternator to get bench tested and it passed, I still swapped it with a new (not reman) alternator and tested it before leaving and it passed. Installed it and same issue.
parts I have thrown at the truck so far:
2 new batteries
New alternator
Water fuel sensor
Alternator plug
Replaced alt to battery cable with a 4 gauge wire
I have also opened the harnesses in the wheel well and chased the alternator plug wires
still getting the lights, batteries aren’t charging from the alternator. What else could it be? Please help!!
Any codes in the ecm?
If you put the leads of an ohm meter between the main stud on the back of the alternator, and each positive battery post one at a time, with the engine not running, how much resistance does the meter read?
With the engine running, using a voltmeter with one lead on the main side on the back of the alternator and the other lead on the alternator case, how many volts does the meter read?
Sorry I haven’t replied. I’ve searched hours and hours on all sorts of forums. Didn’t find anything particular. So after new batteries, alternator, etc, and opening every single harness, I continuity tested the alternator plug and everything checked out fine. Swapped my buddies ecm into my truck and low and behold I have a bad ecm. Now on the hunt for a new one. GM told me they’re on national back order
His is known good and I’ve been using it since yesterday no issues knock on wood
no junkyards around here with lbz parts
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