08 LC200 wont start, need advice

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FGreggo

Joined
Sep 4, 2022
Threads
3
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37
Location
PNW
My 08 decided not to start anymore. Turns over, gets gas, but immediately dies. Pulled the MAF hoping it was a simple fix, but no go.
I hooked up the the code reader and got P0102 P1035. One is for the MAF, the other is for the O2 sensors. All fuses and relays seem to be okay.
Curious on opinions here. Could the O2 sensors be causing the vehicle not to start?
 
How many miles? Fuel pump and/or controller would be high on my list to look into.
 
Bad O2 sensors will usually cause a check engine light but not cause a no start. Any dash lights? It sounds like it’s starting fine, but not continuing to run. I agree with @bloc to look for a fuel delivery issue.
 
bloc said:
How many miles? Fuel pump and/or controller would be high on my list to look into.
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206k. I thought fuel pump too, but it’s getting fuel at each attempt to start.
I’ll dig in a little more this week. I was a little surprised to see the codes pointing to the O2 sensors because I haven't had a check engine light to date.
 
FGreggo said:
206k. I thought fuel pump too, but it’s getting fuel at each attempt to start.
I’ll dig in a little more this week. I was a little surprised to see the codes pointing to the O2 sensors because I haven't had a check engine light to date.
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The pump may still be working but not as well as it should. Meaning there could be enough pressure to kick over but not to remain running. One quirk of our vehicles is that the fuel pump voltage is actively managed to control fuel flow. It could be that voltage is getting stepped down after start and that lower power isn’t enough to keep a weak pump running.

A weak pump could also make it run lean and lead to perceived o2 sensor issues.

This wouldn’t at all be the first time we’ve seen the start/stall behavior, though it doesn’t happen often. Usually with no codes, but not always.
 
bloc said:
The pump may still be working but not as well as it should. Meaning there could be enough pressure to kick over but not to remain running. One quirk of our vehicles is that the fuel pump voltage is actively managed to control fuel flow. It could be that voltage is getting stepped down after start and that lower power isn’t enough to keep a weak pump running.

A weak pump could also make it run lean and lead to perceived o2 sensor issues.

This wouldn’t at all be the first time we’ve seen the start/stall behavior, though it doesn’t happen often. Usually with no codes, but not always.
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I appreciate the info. I’ll likely have to push off draining the tank until next weekend and see if a new pump solves the problem.
 
FGreggo said:
I appreciate the info. I’ll likely have to push off draining the tank until next weekend and see if a new pump solves the problem.
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It's unfortunate we don't have a fuel pressure test port. I'd want to verify fuel pressure before dropping the tank.. I did my pump as PM (and as an experiment to see how worn it was) and while it's far from the worst job, it isn't easy either.
 
bloc said:
It's unfortunate we don't have a fuel pressure test port. I'd want to verify fuel pressure before dropping the tank.. I did my pump as PM (and as an experiment to see how worn it was) and while it's far from the worst job, it isn't easy either.
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Yeah it sucks. I just filled the tank before taking a drive up in the mountains. Still has about 3/4 tank. I still think it’s strange that I had no warning of this coming. I’ve had fuel pumps go bad in the past, and there was always a sign it was going bad.
 
FGreggo said:
Yeah it sucks. I just filled the tank before taking a drive up in the mountains. Still has about 3/4 tank. I still think it’s strange that I had no warning of this coming. I’ve had fuel pumps go bad in the past, and there was always a sign it was going bad.
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Since you have a bit of time before you get going on it do some research here about the fuel pump ECU. It has been a while since we have seen one, and I can't remember whether ~2013 year model was a contributor and possibly corrosion as well, but they do go out occasionally and will have a bit of a different symptom list. I also can't remember whether that would lead to the start/stall you are seeing.. but it's worth looking into.
 
bloc said:
Since you have a bit of time before you get going on it do some research here about the fuel pump ECU. It has been a while since we have seen one, and I can't remember whether ~2013 year model was a contributor and possibly corrosion as well, but they do go out occasionally and will have a bit of a different symptom list. I also can't remember whether that would lead to the start/stall you are seeing.. but it's worth looking into.
Click to expand...
Thank you, I’ll do a little research on that.
 
So the saga ends. I tried resetting the security system just before draining the gas tank, and the truck started up and is running great.
Still going to change the MAF and O2 sensors due to the codes popping up, but the mystery around the start and die has been solved.
Thank you everyone for your input and suggestions.
 
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