Question about Hummer Cars & Trucks
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Posted on Jan 02, 2017
SOURCE: My reverse light stays on
It seems the reverse light switch which is fitted on the gear box has sized to 'on' position, the remedy is to replace the switch.
To male sure its the switch, locate it and remove the connection to the switch thn check it out if the reverse light stays 'on' whn you turn the igntion 'on'.
Posted on May 09, 2009
The driver's Multiplex Control System is a small computer that controls (among many other things) the dash lights brightness, ignition key interlock, shift interlock, and has a tie in to the brake light system and horn relay. It may be that this small computer malfunctioned and started the whole problem chain.
However, I note from the factory shop manual that if polarity is reversed on the shift interlock--it can be damaged. Reverse polarity will ruin the diode inside the shift interlock. This could have happened when you jumped the battery--a brief period of getting the cables and terminals mixed up could have done it.
Checking the shift lock solenoid can be done by removing the steering column upper cover. Disconnect the shift lock solenoid connector (2 terminals). Using long jumper wires, apply battery voltage to terminal 1 (yellow wire side) of the solenoid and ground terminal 2 (green wire side). Check that the shift lever can now be moved out of Park. NOTE: applying voltage in the opposite direction of that above will damage the diode in the solenoid and will probably ruin it. Remove your jumpers and shift back to park and check that the solenoid locks. If the solenoid does not work properly, it will need to be replaced. This involves removing the end of the transmission shift cable and is a complex job. Remember, no power to the solenoid equals a locked solenoid--it takes power to unlock it.
The Multiplex Control Unit has a self diagnostic feature which checks the computer itself and inputs to the computer. The computer check is called mode 1 and the input test is mode 2. The diagnostic trouble codes are outputted to the ignition key light and beeper.
To test, first confirm that all fuses are good, especially fuse 9 (10A) in the driver's under dash fuse box (left kick panel) and fuse 13 (7.5A) in the passenger's under dash fuse box (right kick panel). Then use a jumper wire (a wire with small alligator clips on each end works best) to jump the two leads of the multiplex test connector. (This is a light green 2 terminal connector dangling from the same wire bundle as the brake pedal switch connector.) Buckle the driver's seat belt (avoids nuisance beeps). Now turn the ignition switch to on. After about 5 seconds, the ignition key light should come on and the beeper should beep for 2 seconds then stop for .2 sec. then beep once for .2 seconds. This indicates that the system is in diagnostic mode 1.
If no diagnostic trouble codes (DTC's) are present, the key light and beeper will not blink/beep again. If there are codes: about one second after entering mode 1, the key light and beeper will indicate the DTC and repeat it every 3 seconds. If there are more than one, the system will indicate them in ascending order. The codes will be a light flash and beep so you will have to count the flashes/beeps to keep track. The codes range from 1 to 6. Code 3 (three flashes/beeps) indicates a problem with the multiplex control unit itself. Write back here for other codes or for questions about mode 2.
Posted on Jan 24, 2011
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May 08, 2016 | 1977 Triumph Stag
Feb 21, 2016 | 2009 Hummer H3
Feb 26, 2014 | 2007 Jeep Compass Limited
Hello Stacy, My name is Mike. I am thrilled that you choose
me to help you with your problem. I am sorry, it took me a few hours to get back
to you. I have been helping other customers. Here is where I am with this on
your cranking and not starting issue. Oh, by the way great job on your part
eliminating some of the other potential suspects.
First of all, I try and tackle the easiest things first,to
see if we get lucky.
Pull the start/run
relay out for a couple minutes, then put it back in and reset it might reset the
passlock box and start right up.
Now, why did I say that? I believe your problem is with your
Passlock indicator.( which has to do with your anti theft system)The way I just
described is a 50/50 chance to have it work, but don't worry. I always have a
plan B and C.
Here is some questions to your symptoms: Stay with me now,
wait for it.
Turn ON the ignition, with the engine OFF.
Attempt to start the engine, then release the key to ON
(vehicle will not start).
Observe the SECURITY light, after approximately 11 minutes
the light will turn OFF.
Turn OFF the ignition, and wait 10 seconds.
Repeat steps 1 through 4 two more times for a total of 3
cycles/30 minutes ( the vehicle
is now ready to relearn the Sensor Data Code and/or passwords
on the next ignition switch transition from OFF
Important: The vehicle learns the relearns Sensor Data Code
and/or password on the next ignition switch
transition from OFF to CRANK. You must turn the ignition OFF
before attempting to start the vehicle.
Start the engine (the vehicle has now learned the Sensor Data
Code and/or password).
Here is Plan C as promised, but I personally would not
suggest, Even though GMC offers a bypass procedure.
Link for a Bypass Solution:
Plan D, would be have to check into possibility of bad ECM,
but lets hope that is just a worst case scenario.
Thanks So Much,Mike. Please Keep Me Informed of progress.
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