20 Most Recent 2004 GMC Envoy - Page 5 Questions & Answers

Did the shop duplicate the no start? Does the engine crank over but not fire or does it not crank over (do you hear the starter engage). Your post lacks important details about things like what the OBD2 fault code testing showed, does it have fuel pressure during the no start (if engine does crank over) does it have spark when it cranks but will not start?

I want to see if i catch your drift ! When you turn the key in the ignition switch to start , nothing happens ? Have you tried moving the gear slector to the neutral position to see if it starts then ? Park neutral safety switch problem , maybe . Here is a description of how it works or how it's suppose to work . Circuit Description (ECM/PCM Controlled) Moving the ignition switch to the START position sends a 12-volt signal to the engine control module (ECM)/powertrain control module (PCM) Crank Request circuit. The ECM/PCM verifies that the transmission is in the PARK or NEUTRAL position. With the transmission in Park, voltage flows through the Park/Neutral position switch and feeds the starter relay coil. The PCM then grounds the control circuit of the starter relay. When the starter relay is energized it allows battery positive voltage to the starter solenoid S terminal. On some vehicles the starter will continue to crank the engine with the key released until it starts or the crank command has timed out to prevent excessive heat build up in the starter circuitry or the ECM/PCM receives an engine run flag. Circuit Description (BCM Controlled) Moving the ignition to the START position signals the body control module (BCM) that engine crank has been requested. The BCM verifies that theft is not active and sends a serial data message to the powertrain control module (PCM) requesting engine start. The BCM also energizes the RUN/CRANK RELAY. When the RUN/CRANK RELAY switch side closes, and the vehicle is in Park or Neutral or with the clutch is fully depressed, if equipped, supplies voltage to the starter relay coil. The PCM verifies the transmission is in Park or Neutral and the clutch is fully depressed, if equipped. The PCM will then ground the control circuit of the starter relay, closing the switch supplying voltage to the starter solenoid. On some vehicles the starter will continue to crank the engine with the key released until it starts of the crank command has timed out to prevent excessive heat build up in the starter circuitry or the PCM receives an engine run flag.

The throttle body needs to be cleaned, grime in this area prevents the throttle plate from closing completely and allowing air to enter, making the air/fuel mixture lean.

7 Quarts

The parts prices are $36 thermostat and depending on fan clutch model $88 - $260 From autoparts warehouse site which leaves $580 for draining system and replacing parts and refilling system plus time a bit steep get another quote from a different mechanic and decide

if it auto transmission , the ratio changes and the speedo reading is affected by the VSS sensor ( around $100 from reports) if the transmission is running well other than that it will not need a transmission just and transmission oil change suggest that you find an accredit professional transmission shop and have a proper diagnosis done

Check the oxygen sensors.

With this info, I'm betting motor mounts. If they're bad, make sure and use AC Delco brand. Other brands will tend to crush easier, now you're back with the same problem.

It's a short in the instrument cluster. I had the same problem with my 2004 XUV. It started in early December of 2007. Intermittent manifestations, than more persistent. Took it to the GMC Dealer -- Of course, the Truck wouldn't do it's tricks for the Tech. They replaced the ignition switch and sent me home. It got progressively worse. I waited until I was sure it would do it for the tech. Took it back in to GMC Dealer-- It's a short in the instrument cluster. They needed to replace the entire cluster. I bought an extended warranty when I bought the truck. The warranty is still in effect -- So I only had to pay the $100 deductible. No Idea what it might cost otherwise.

1 side of the fuse is ground. Ck emissions, clogged exhaust, throttle positioning sensor, fuel PSI, vacuum leaks. Scan the PC for codes & go from there