02 Suburban - died and won't start

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#1
2002 Chevy Suburban Z71 4X4 5.3L flex fuel. My wife was driving along and then it just died. So I checked fuel pressure at the system bleed valve and there was none. Fuel gage reads empty and low fuel warning message is on. Maybe she ran out of gas? I put in 10 gallons and it still won't start. I notice now I can't hear the pump run when I put the key on so I tow it home and I replace the fuel pump - it still won't start. I checked the fuel pump relay and there is no power going to the coil side when I put the key on. I can however jumper the relay socket on the fuel pump power side and the pump runs and pressurizes the system. But it still won't start when I try that and turn the engine over. No codes from the ODBII scanner or SES light. Fuel gage still reads empty with the low fuel message even with 10+ gallons in the tank .

I figured maybe an anti theft system issue since that disabled the fuel pump so I did the reset procedure (key on 10 minutes, then off 10 seconds, repeat 3 times) and the security message isn't flashing and it died while the engine was running so I don't think that is the problem but what do I know. Do you think it still could be an anti theft issue?

Do you think I should replace the PCM or give up and just have it towed to the dealer and let them figure it out? What is involved in replacing the PCM? Do you think a PCM problem could cause the fuel gage/low fuel message problem too?

Is there anything else that I am overlooking? Are there fuses anywhere for the coil side of the fuel pump relay I can look for?

I have the factory service books and they say to reprogram the PCM after replacement. Can I do that without special tools? Can I get a PCM that is already programmed? Can I switch out the programming chip from one PCM to another?

And just exactly how does one remove those electrical connectors from the PCM? I tried pulling them off and they were budging. I don't want to break them off by accident.


Thanks for any help.

John in San Antonio
 
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#2
Did you check all the fuses?.How about a different fuel pump relay?....Here is a diagram of where the fuse is....Jim

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#3
Give the fuel tank a good smack with either the palm of your hand or a rubber mallet. If the brushes are stuck you might be able to get it to run. Just beware, if this makes it start it might not start again when you stop the truck.

Ford_Dude
 
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#4
It isn't the pump. The pump is fine - brand new as a matter of fact. Jumpering the fuel pump relay socket causes the pump to run. It's not the relay, the PCM isn't powering up the relay on the coil side, verified with a multimeter. Also swapping the relay out with an identical one that works (like the horn relay) confirms that. I see by the schematic diagram you attached Jim there is no fuse on the coil side of the relay and the relay is directly connected to the PCM, which was one thing I was curious about. Seeing the fuel gage outputs from the PCM to the instrument cluster also casts some suspicion on the PCM in my mind. What is involved in buying a new PCM and replacing it?
 

Gus

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#5
First thing you need to do, is get a scanner and see if you can even communicate with the VCM......if you can, then see if there are any codes.......if you can't communicate with it, there could be a power, ground, serial data, or VCM problem...

You may be jumping the gun on a VCM.....get it diagnosed......you already put in a fuel pump, you may not have needed, if the problem was it wasn't getting any power....
 
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#6
Yup. Fuel pump I didn't need. Dumb.

I checked with my $150 ODBII scanner and it communicated and there weren't any codes set.
 
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#7
slow down on the parts replacing/......
especially VCM/CM

you need to let us know,
1) is vehicle stock??.......Hopefully that fuel pump was AC delco...
2) SErvice engine light staying on? does it self test on stqrt?
3) security light staying on?? does it self teston start?
4) remote starter??

ECM B fuse 20 amp.....?

  FYI: Normally the fuel pump will only be energized for @3seconds when key moved to run/start.. Will your scan tool do ALL modules for codes - BCM?  VATS?

I think there is one more puzzle piece we are "missing"
 
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#8
Yes, vehicle is stock. 100K miles on her and I bought it new off the train before it ever arrived at the dealership and it has been babied. Never had any serious trouble with it before so it hasn't been butchered or messed with. No SES light. No security light. Don't know about the self test. I pulled all the fuses I could find and looked at them.

Fuel pump circuit doesn't energize when turning key to "run". I know it normally runs for about 3 seconds if I don't switch it to start. Voltage on the FP relay energizing side momentarily hits about .1 V before going to 0 when you put the key in "Run".

My scanner won't check BCM or VATS.

Wife used to tell me that the truck would momentarily stop running when she was driving around town from time to time in the past, but it never happened to me and it always ran great and never threw any codes that would light up the SES light for me so I thought she was imagining it. Perhaps not now that this happened.
 

brcidd

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#9
How about your ignition switch-- does the pink wire have 12volts when key turned to run? with gages inop- and no fuel pump- I suspect ignition switch--
 
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#10
Checked fuses again. Found that the 10 amp ECMI fuse was blown. I probably didn't check it before and just thought I did. Replaced it and it started right up. I wonder what caused the fuel to blow.

But the fuel gage still doesn't work and the warning says low fuel. I found this TSB: TSB #010604036 -- DIAGNOSING FUEL GAUGE READING EMPTY, LOW FUEL MESSAGE DISPLAYED

Anybody happen to know what they tell you to look for there?