Help- engine shuts off after starting (1 Viewer)

[canyonrider]

I just had to get my 2009 LC towed after the engine wouldn't start. Thought I would post here for some troubleshooting ideas while I wait for the shop to look at it on Monday. Short version: engine turns over and roars to life...for about two or three seconds, then dies. If I try to start again immediately, it struggles to turn over for a bit but then doesn't start at all (engine "choking" sound, not the empty click click click of a dead battery).

Longer version: I used the LC this morning to tow a trailer to the tire shop (for installation of new trailer tires). First odd symptom: when I started it up this morning, I noticed that the front passenger seat heater light was on, even though the seat heater was turned off and not heating (I had left driver seat heater on, and it was lit up/working as normal). LC drove absolutely fine taking the trailer to the shop and back, no issues other than that heater light staying on. No one from the tire shop drove the truck, I just pulled it in and out so they could install the trailer tires.

When I arrived home I backed the trailer into the driveway, then shut it off to unhitch. But then I needed to reposition the trailer, and when I went to start up the LC again I had the issue described above. Engine started for a moment, then shut off, then tried to turn over but wouldn't start. I tried this a couple of times with the same results. Called for a tow, and fortunately I was able to unhitch from the trailer without moving the truck any more.

Any ideas as to the cause of this? Other info that may/may not be relevant: 155,000 miles on the truck, owned for nearly five years, 110,000 miles on it when I purchased. A couple of years ago I had Slee install a new starter and radiator as preventative maintenance. New battery installed about 2.5 years ago. Zero issues like this before, today was the first time. Car has been sitting more than usual over the past year, but I'm still driving it every week and just drove it up to Leadvillle two weeks ago in bitter cold temps with no issues. Today was the first day towing (brake controller and 7-pin used) since November.

My random initial theories include alternator, fuel pump, or some electrical/wiring issue. But I'm no expert, thought I would see what the internet troubleshooters think. TIA.

 

[04UZJ100]

I bet it’s the battery. These things do weird things when a battery is on its way out.

 

[gaijin]

You do have enough (> 1/2 full) gasoline in the tank, right?

 

[canyonrider]

You do have enough (> 1/2 full) gasoline in the tank, right?

Yep, at least 3/4 full, filled up a few days ago.

 

[Sandroad]

Any water where it shouldn't be? Check the floor on the drivers side and everywhere under the dash and bottom of the A pillars. Electrical issues have been reported from leaking windshield replacements and clogged sunroof drains allowing water into junction boxes and connectors. I agree with @04UZJ100 you need to check out the battery, but if it's ok, my bet is on water in the wrong place.

 

[canyonrider]

Good thought on the potential water issue. We had nearly a foot of snow here early in the week, and then it warmed above freezing yesterday and today with lots of fast melting. I replaced the windshield in 2018 and hadn’t seen any issues, but then again we haven’t seen a lot of precip here in the last couple of years. Thanks for chiming in.

 

[canyonrider]

Following up on this in case others have a similar issue: the dealership diagnosed it as an immobilizer system malfunction. They suspected an issue with the interface between the key and immobilizer (the key I was using appears to be a replacement key acquired by a previous owner, and it was never "registered"). The dealer reprogrammed both keys and now the truck is starting and running fine. Battery is in good shape.

The seat heater light is still on though, regardless of switch position. Dealer claims this is just a coincidence with the immobilizer failure and that it is probably a switch/light issue. I'm a little more skeptical given the timing and lack of history with it happening. Weird that it started doing it on the same morning the immobilizer caused problems.

 

[Sandroad]

Following up on this in case others have a similar issue: the dealership diagnosed it as an immobilizer system malfunction. They suspected an issue with the interface between the key and immobilizer (the key I was using appears to be a replacement key acquired by a previous owner, and it was never "registered"). The dealer reprogrammed both keys and now the truck is starting and running fine. Battery is in good shape.

The seat heater light is still on though, regardless of switch position. Dealer claims this is just a coincidence with the immobilizer failure and that it is probably a switch/light issue. I'm a little more skeptical given the timing and lack of history with it happening. Weird that it started doing it on the same morning the immobilizer caused problems.

Glad it’s running ok and thanks for the report back. There are a couple things that are odd. A key won’t work unless it is programmed (registered) to the vehicle. It’s possible the key had a glitch and needed reprogramming, but after 5 years and 45K miles with you, I doubt it. Maybe it was just a bad fob battery. The coincidence with the seat heater failure is too much to ignore. I would still look for water inside and check all battery connections.

 

[canyonrider]

Agree, seems like there’s a bigger electrical issue that’s in line with some other threads on this issue. I noticed that the seat heater light is staying on constantly, even with the vehicle off and locked.

I removed the plastic cover under the glove box and it was dry (dusty, even). Good. Tested the sunroof drains and they seem to pass water through to the ground quickly. Also good.

Then I removed the narrow door/kick panel that runs along the passenger side floor. Found a small amount of water in there, towards the rear (i.e. not up near the harness connections at the front). Guessing that came from melted snow from the passenger side. Not sure if that’s enough to cause a problem, there don’t seem to be any connections in that area.

I tried to remove the same panel on the driver’s side, but it’s a tighter fit and my hands were getting cold so I quit. Taking the truck to a reputable local shop this week for front brake pads and asked them to investigate this issue, I’ll update again later this week.

 

[bigredmachine]

A key won’t work unless it is programmed (registered) to the vehicle. It’s possible the key had a glitch and needed reprogramming, but after 5 years and 45K miles with you, I doubt it.

you are correct that the key has to be programed for the truck to run but i have seen a few keys that just stopped working, being an aftermarket key may also be a factor.

I noticed that the seat heater light is staying on constantly, even with the vehicle off and locked.

try switching the switches between the driver and passenger side and see what happens. if the passenger side stays on all the time than its going to be most likely in the switch, the switch is the controls for the seat heater so if theres an issue its most likely in the switch.

 

[RET2]

Agree, seems like there’s a bigger electrical issue that’s in line with some other threads on this issue. I noticed that the seat heater light is staying on constantly, even with the vehicle off and locked.

I removed the plastic cover under the glove box and it was dry (dusty, even). Good. Tested the sunroof drains and they seem to pass water through to the ground quickly. Also good.

Then I removed the narrow door/kick panel that runs along the passenger side floor. Found a small amount of water in there, towards the rear (i.e. not up near the harness connections at the front). Guessing that came from melted snow from the passenger side. Not sure if that’s enough to cause a problem, there don’t seem to be any connections in that area.

I tried to remove the same panel on the driver’s side, but it’s a tighter fit and my hands were getting cold so I quit. Taking the truck to a reputable local shop this week for front brake pads and asked them to investigate this issue, I’ll update again later this week.

Have you considered pulling that fuse that serves that switch to A. prevent any battery drain and B. to possibly prevent any possibility of it causing further issues? Guess B. should be A. sorry.

 

[canyonrider]

Checking back in. My mechanic found that the passenger seat heater switch was partially sticking, and didn't identify any kind of water intrusion issue elsewhere. The seat heater light seems to be operating normally after "unsticking it," so hopeful that this is all resolved. I'm still going to be keeping a close eye on things after any kind of snow/rain, really don't like how the immobilizer issue popped up out of nowhere.

 

[Lester did that]

Checking back in. My mechanic found that the passenger seat heater switch was partially sticking, and didn't identify any kind of water intrusion issue elsewhere. The seat heater light seems to be operating normally after "unsticking it," so hopeful that this is all resolved. I'm still going to be keeping a close eye on things after any kind of snow/rain, really don't like how the immobilizer issue popped up out of nowhere.

I have the same year. Had the same issue with the passenger seat heater light staying on when it was turned off even when the car was turned off. I just let it go. There where times it sat the whole weekend. Monday morning the light was still on but it fired right up. It sat for a week once and never a problem with battery drain. I don't know what the issue was but what fixed it was when I had a passenger that turned it on I left it on. When I got in the next day the light was on so I just said oh right let me turn that off no one is sitting there. The light went off. It's been fine for over a year. No idea? Gremlins for sure

 

[RET2]

I have the same year. Had the same issue with the passenger seat heater light staying on when it was turned off even when the car was turned off. I just let it go. There where times it sat the whole weekend. Monday morning the light was still on but it fired right up. It sat for a week once and never a problem with battery drain. I don't know what the issue was but what fixed it was when I had a passenger that turned it on I left it on. When I got in the next day the light was on so I just said oh right let me turn that off no one is sitting there. The light went off. It's been fine for over a year. No idea? Gremlins for sure

And they want us to go all electric? Wait till the electron insurrection.