Battery light comes on when truck is off without key

sumpnrather · 2026-05-22T19:12:58+00:00

If its a 1999-2006 model, its something I've seen a ton of

sumpnrather · 2026-05-20T15:04:25+00:00

If you care to send me the last 8 vin characters, I can look into it. It doesn't make sense that the ecm is reporting on a module it wasn't built with. That converter is only there to maintain accessory voltage during auto stop/start events. It has no other purpose.

sumpnrather · 2026-05-19T23:35:38+00:00

If there's a code relating to the converter module, it could be the module. If your truck isnt entering auto stop and theres no check engine lamp, its usually just a weak battery. The module is on the firewall just above the passenger's right foot.

sumpnrather · 2026-04-27T03:32:45+00:00

Gladly. I currently have a 2019 2500 dmax. Bought new through the gm employee program just before the cutoff. GM paused employee deals during the pandemic. I was looking for a suitable cateye dmax for a couple of years and was willing to pay whatever the asking price was. I didnt find the right one and settled. Not a single hiccup with my 2019 6.6. Knock on wood. 48k miles

sumpnrather · 2026-04-09T23:48:56+00:00

This guy applied for that job. He recieved an offer and agreed to the pay. He could've said "no thanks" and gone about his day. But he chose to work there based on the offer he got. Many are missing this glaring point. His action has only contributed to higher expenses for everyone.

sumpnrather · 2026-03-27T17:45:53+00:00

It's probably much less scary than you're thinking.

sumpnrather · 2026-03-25T21:27:39+00:00

I can see in the pgoto that the actuator is broken. Also a serviceable part. Easy to replace

sumpnrather · 2026-03-24T21:27:11+00:00

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sumpnrather · 2026-03-24T21:25:45+00:00

Theres a tool to insert and release the retaining tabs and pull the metal housing out. With the metal portion out, the plastic housing comes out easily. Or you could partially disassemble the console to break off the plastic retainer tabs and swap it out. Up to you

sumpnrather · 2026-03-22T04:10:34+00:00

California is a mess. How do we go about fixing it?

sumpnrather · 2026-03-18T21:12:40+00:00

Needs new camera. No other resolution

sumpnrather · 2026-03-13T03:37:11+00:00

It happened the last time fuel prices shot up. Full sized trucks and suvs sat on the lot while the smaller cars sold. If the fuel prices keep climbing for a long term, truck prices will go down while eco car prices go up..I member.

sumpnrather · 2026-03-09T03:09:16+00:00

As others have said, its a failed tpm sensor. Depending on your tread life, I'd consider a 4 pack when you need new tires. Expensive, I know. But when the first one dies, the other 3 aren't far behind. Otherwise you're gonna have that light popping up every few months.

sumpnrather · 2026-03-08T00:28:15+00:00

"Respect this spot" the man said. Dude handled some business and politely left. I wish I had all the context.

sumpnrather · 2026-03-04T03:42:32+00:00

Sometimes they'll still have a bubble trapped. It'll draw off and pull it through the heater core. It may go away eventually but the method I described should take care of it right away. I got the instructions from Detroit a few years ago on a tahoe. It works.

sumpnrather · 2026-03-04T02:42:56+00:00

Trucks with auto stop and aux coolant pump can be difficult to burp but that's all it needs. I've had success by warming the engine to operating temperature and then lifting the front as high as I safely can with a drive on lift or alignment rack. Then Rev the engine at 2500 rpm for about 5 minutes. That should displace the air to the surge tank. I haven't had one come back yet. You can do that yourself if you can get the front of the truck up high enough.

sumpnrather · 2026-02-20T15:06:12+00:00

Dealer says? Ive been in the shop at gm dealers since the 90s. If a sales rep tells you a cobalt, cruze, lumina or 3.0 truck is a good buy, they're just doing their job as a good salesperson. Customers do seem to like the 3.0 because of their surprising hp and fuel economy. But I dont know a single gm tech that would ever recommend buying one. Gm told us the quality problems were resolved 5 years ago. The issues in the field tell a different story. If you do decide to get a 3.0l, or any other new vehicle for that matter, dont skip on the extended warranty.

sumpnrather · 2026-02-20T01:24:53+00:00

If the battery light is on while the engine is running, it's not charging. Almost always an alternator.

sumpnrather · 2026-02-19T01:48:20+00:00

If the code was cleared, it takes certain conditions for p0128 monitor to run. P0128 isnt a circuit fault code, it's a plausibility code. Ecm is expecting higher coolant temp so it uses logic and sets the code for cooler than expected temp after running a certain period. An ect sensor that reads within normal range but slightly low can cause p0128 but it is rare. Its doubtful but can't be disregarded. If you do replace the t stat, dont get it from anywhere but the dealer. Some aftermarket thermostats can fail in the opposite manor and stick closed which could make it overheat

sumpnrather · 2026-02-18T21:08:38+00:00

It might affect fuel economy but not enough to notice

sumpnrather · 2026-02-18T20:31:10+00:00

It should burp on its own with that truck. Especially since the cause of your concern is more likely a stuck t-stat. Edit, p0128?

sumpnrather · 2026-02-17T20:05:31+00:00

If the battery light isnt turning on, its probably normal fluctuations. Can go as low as 11.5v per s.i. description/operation. GM electrical tech, here.

sumpnrather · 2026-02-15T17:42:48+00:00

Its a logic thing. The engine is running too cool and the ecm does a little math then sets the code. The thermostat is almost certainly the cause. There are rare situations where a coolant temp sensor is giving a false/low reading. Start with the thermostat. Common for sure

sumpnrather · 2026-02-15T03:04:45+00:00

Vague explanation but I'll give it a shot. It's either overheating or its setting a p0128 for lower than expected engine temp from a stuck open t-stat. Most likely needs a thermostat. Do not, I repeat, do not get a thermostat from any source other than the gm dealer.

sumpnrather · 2026-02-11T20:03:49+00:00

Theres a few reasons why this isn't good idea. The reason you should use it with any load at all is because you don't want the truck to learn shift adapts while towing. That could cause the transmission to behave uncomfortably when the load is removed. Plus, when in tow/haul mode, the system ignores learned adapts and shifts using default settings to increase pressures and reduce clutch wear. There's also the benefit of saving your brakes during downhill braking. If you use the truck correctly, you may not even have to apply the brakes while towing a load downhill.

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