GMC Troubleshooting Questions? Ask a Mechanic for Answers
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If you can check and make sure there is no debris or contaminants in the fuel itself.In some cases if the fuel is contaminated with debris or a substance that isn't fuel like water the fuel pressure will be o.k. but the engine will not start or run properly when it does start.If this was already checked and found to be o.k. let me know so we can continue.
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This model does use a security feature and it is actually part of the electronic ignition switch itself.From the electronic ignition switch there is a single or two wire sensor that seats into the top of the ignition cylinder housing.This is a plunger type sensor that the plunger is depressed with the correct key in the ignition and the ignition rotated.If this plunger breaks off (which is common) then the electronic ignition switch needs replaced.This needs checked to see if it is broken with this switch needing replaced to correct this fault here.
You can try this relearn below as this is the security relearn for this model.You can skip the steps of clearing out the fault codes as this isn't needed to do this relearn here.
REPROGRAMMING PROCEDURE The following is the Auto Learn Procedure: 1. Insure the ignition key is in the ON position. 2. Clear all Passlock(TM) Module and VCM/PCM DTCs. 3. Momentarily rotate the ignition key to the CRANK position (Do NOT start the vehicle), then release it to the RUN position (Do NOT key OFF in the process). 4. Wait 10 minutes. Observe the SECURITY indicator. Refer to the following list for the appropriate responses: ^ If the Passlock(TM) sensor was replaced the SECURITY indicator will flash for the 10 minutes duration. ^ If the Passlock(TM) Module was replaced, the SECURITY indicator will flash for a few seconds and then remain ON for the remainder of the 10 minutes duration. ^ If the VCM/PCM was replaced with a new programmed VCM/PCM and connected to the vehicle for the first time, the vehicle will start and this procedure may not be necessary. ^ If the replacement VCM/PCM was connected to any vehicle at any other time, even momentarily, the SECURITY indicator will flash for a few seconds and then remain ON for the 10 minutes duration. 5. The SECURITY indicator will transition from flashing to ON briefly to OFF after 10 minutes if remaining in the ignition ON position. 6. Turn the ignition switch to the OFF position and wait for 10 seconds. 7. Repeat steps 3-6 two more times. The new security code is ready to be communicated among the Passlock Sensor, Passlock Module and VCM/PCM. The new password ***** ***** on the next ignition lock cylinder cycle from OFF to CRANK to ON (start attempt).
O.k.,if you can remove the steering column covers especially the top cover behind the steering wheel and there should be a small plunger sensor that seats into the top of the ignition cylinder housing.There is a tab that you press inward on the side of the sensor to then rotate the sensor and remove it.See if the little plunger ball is worn off.If it is then the ignition switch itself needs replaced and will cause this here.It should look similar to this here.If you look at the small whitish sensor behind the pick in the diagram here this is the plunger that fails.https://www.dropbox.com/s/6a65i5ufbw81fnu/Ignition-Switch-31-11-04.png?dl=0