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marc 5/12/2010

1999 GMC W3500 Forward W3S042 8 Cyl 5.7L


why wont it stay running

it starts every time......turn key and it starts everytime..let the key go and it stops.................it will run on the fuel that it gets when you turn the key. starts and runs for a second. fuel shoots up about 4 inches from the valve on the line.........fuses are good..with key on .............. the fuel gauge moves back and fourth about a quater...when it runs for that short time the dash lights go out........... except the security light ????????????????????????

1 Answer


HouseCallAuto 5/12/2010

If the security light is on or flashing the reason it will not stay running is because the security module sees an incorrect input signal. The most common cause is a bad PassLock sensor. You can try this relearn procedure but if it solves it and then repeats the same thing again soon you will need to replace the Passlock sensor and housing.>>

1. A theft relearn procedure must be performed. Try to start the vehicle and let it stall. Then leave the key in the run position for 10 minutes minimum.

2. After the 10 minutes, shut the key completely off and wait 20 seconds for everything to power down.

3. Then try starting it again, and if it stalls once more, do a 10-minute key on wait again.

4. This whole procedure must be done 3-4 times in a row to complete the relearn.


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