IFICKSSTUPH

Hey all,

03 express 2500 6.0 started running funny then I got 0300missfire, 101 MAF performance,463fuel level sensor cir high voltage,522 oil pressure sensor circuit low voltage,1125 tp sensor low voltage,1380 misfire. Where to start? Oil pressure sensor is new. I'm wondering where all this might intersect so I can start there. i imagine they all run into one harness . New to express vans. Any help appreciated.

mountainmanjoe

lots of voltage problems. get your battery + alternator load tested for free at Autozone

MitchM

OP, he Chilton manual, $19.95 at auto parts stores is a good starting point for understanding what the P codes mean. if your battery load test and alternator are fine, you still might have a corroded ground which is ruining the signal voltage . A good GM dealer can give you some possible diagnoses. I have had a devil of a time getting a cure for a p0300 random misfire , despite them collectively following all of mountain man joe's suggestions (work done by 4 different mechanics, including a chevy dealer.) search on this board for express p0300 misfire for the sorry story.

IFICKSSTUPH

Looked at the wiring diagrams. Seems to all be 5v circuits from what the mechanic said. Do these have a common ground? Do they all run through pcm? Replaced the oil pressure switch with Delco part and it burnt after a day of driving. There's gotta be a common factor between these circuits.

mountainmanjoe

There are many grounds, usually grouped by location, and not far from each sensor. You would have to get detailed schematics and component location charts.

IFICKSSTUPH

I've been banging my head against the wall with this. Hooked up a scanner to see live data. I've noticed that as the engine warms up, voltage slowly drops. Starts off at 14.5 cold then progressively drops to 13.57/13.67 at idle. Is this normal? It doesn't drop much when I turn on a/c hazard lights and high beams.

IFICKSSTUPH

Also, oil pressure sensor has pegged at 80. It's a new Delco part about 3 days old.

Voltage regulator maybe? I've chased every ground I can find. Chilton diagrams are limited at best. Any resources for detailed schematics with locations?

mountainmanjoe

Yes, that's normal voltage.

Your local public library may have subscriptions to service data.

William Kisselstein

There's a deal with a piece of foam in the oil pressure sensor that gets loaded up with crud and causes bad readings, might be worth checking to see if that applies to your model year.

Isn't there an upfitter guide with wiring diagrams for these vans, intended for people who convert them, you can look at for free?

Alternator is going to be internally regulated on this.

Common failure is a braided ground strap underneath from engine to frame, they corrode and turn basically into dust. But that's a full voltage circuit.

If the PCM is still on the left inner fender like it is on 02-back Express, the whole case can corrode and cause all kinds of strange problems when water gets into it. I would at least examine that. It's primarily an issue in the salt belt.

mountainmanjoe

I don't think upfitter schematics go back to '03. But you're welcome to check gmupfitter.com
In later models , voltage is regulated by the ECM. I do not know what year that changed.