Top 10 1998 GMC Sierra Questions & Answers

You may have a problem with the contacts in the ignition switch (not key part), when you crank the engine a signal is sent to the fuel pump to run, when it starts and you let off the key another set of contacts keeps the pump getting power Through a relay), these are known as crank and run modes.

>>>>FIRST disable the air bag system
You'll need to remove the upper and lower steering column covers.
Also all the trim under the drivers side, kneee bolster, etc...
The ignition switch has 2 screws holding it on.
Remove those screws and all related wiring harness.
Then the switch.
Here is the procedure from GM......

Place the multifunction lever in the center or the OFF position.
Caution: Unless directed otherwise, the ignition and start switch must be in the OFF or LOCK position, and all electrical loads must be OFF before servicing any electrical component. Disconnect the negative battery cable to prevent an electrical spark should a tool or equipment come in contact with an exposed electrical terminal. Failure to follow these precautions may result in personal injury and/or damage to the vehicle or its components.

Disconnect the battery negative cable.
Disable the SIR system.
Remove the steering wheel inflator module.
Remove the horn plunger contact.
Remove the steering wheel.
Remove the tilt wheel lever.
Remove the ignition lock cylinder. Remove the upper steering column trim cover.
Couldnt find a diagram. Hope this helps.

Its fairly easy, you dont have to replace the fittings at the cooler. if they are leaking up at the cooler, it needs to be replaced, but if not, its just simple line to line, not too long of a process

please rate well! hope this gives you the info you needed!

I had this same P1345 code on my 1998 GMC K1500 5.7 for about 2 years. Each time the code was erased, the "Service Engine Light" came right back on with the same code. I tried replacing the cam sensor, but that didn't solve it. I had the timing adjusted, it was out -13 degrees. After adjustment, the "Service Engine Light" went off, but only for a short time. Adjusting the timing is just a temporary mask on fixing the real problem and eventually you will run out of adjustment. I read about this same problem on another forum and someone recommended changing the distributor gear. So I checked the gear and a the teeth were worn. Replaced the gear ($35 part), readjusted the timing and the light has been off ever since. Apparently the gears in 96-99 are soft and wear enough to throw off the timing. This code is telling you the crank and distributor are out of sync. So before you start buying sensors and other misc. parts, try the distributor gear if you are getting a P1345 code.

Note, removing the upper intake manifold is not necessary when removing lower intake manifold, they are removed as an assembly.
Disconnect negative battery cable. Drain cooling system. Remove air cleaner assembly and inlet duct. Mark and remove distributor. Remove upper radiator hose at thermostat housing. Disconnect accelerator and cruise control cables. Remove heater hoses from intake manifold. Remove EGR pipe.
Disconnect fuel lines at rear of engine. Remove AC compressor and set aside(leave hoses connected). Remove canister purge solenoid. Disconnect theSCPI injector, ignition coil, Ignition Control Module, generator,IAC motor, TP sensor, O2 sensor, Exhaust Gas Recirculation valve and Engine Coolant Temperature sensor wiring harness connectors. Remove PCV valve and hose. Remove lower intake manifold bolts. Remove lower intake manifold.
Installation.
Always use New O-rings when reconnecting fuel lines at rear of engine. Apply a bead of RTV silicone sealer along the front and rear sealing surfaces of the block.See Fig.6. Install new gaskets and intake manifold on block while RTV is still wet to the touch. Use Threadlock 12345382 or equivalent to lower intake manifold bolts. Tighten lower intake manifold bolts in sequence to specification table. See fig. 7. To complete installation, reverse removal procedure.

One way is to remove any fuses that say ECM/PCM in the fuse block and let them out for 20 minutes or more and another way is to disconnect the negitive battery cable and touch it too the positive. or pull all the connectors off the pcm.

GMC Silverado also called Sierra, Chevrolet Cheyenne and GMC Sierra Denali (only Mexico)
- Vehicle Wiring
- Wire Diagram GMC
- GM Full-Size Trucks 1988-1998 Repair Information (free register)

I hope helps with this. Good luck (remember rated this help).

The v-8's timing is supposed to be 0 degrees plus or minus 2 degrees and is only adjustable if you have a scanner. A timing light does not work on them.
These engines can be "timed" in the way you are used too.
The distibutor housing holds the cam sensor, The PCM calculates the timing by measuring the crank signal and the cam signal.

What you are seting by turning the distibutor housing is the correlation between the 2 sensors. On the V-6 model, the housing holddown bracket is fixed to the housing so if you return the rotor to the proper position when reinstalling the housing, the engine should be at the correct cam sensor position setting.they did not fix the holddown bracket to the V-8 models, it would have saved a lot of headaches.
To set the correlation between the 2, you will need a scan tool that can read camshaft position offset. With the engine RPM over 1200 adjust the offset too 0 degrees.
TEST PROCEDURE
The ignition timing cannot be adjusted. The distributor may need adjusting to prevent crossfire. To insure proper alignment of the distributor, perform the following:

With the ignition OFF, install a scan tool to the DLC.
Start the engine and bring to normal operating temperature. IMPORTANT: Cam ****** Offset reading will not be accurate below 1000 RPM.
Increase engine speed to 1000 RPM.
Monitor the Cam ****** Offset.
If the Cam ****** indicates a value of 0°+/-2°, the distributor is properly adjusted.
If the Cam ****** does not indicate 0°+/-2°, the distributor must be adjusted.

ADJUSTING PROCEDURE
With the engine OFF, slightly loosen the distributor hold down bolt. IMPORTANT: Cam ****** Offset reading will not be accurate below 1000 RPM.
Start the engine and raise engine speed to 1000 RPM.
Using a scan tool monitor Cam ****** Offset.
Rotate the distributor as follows:
4.1. To compensate for a negative reading, rotate the distributor in the counterclockwise direction.
4.2. To compensate for a positive reading, rotate the distributor in the clockwise direction.

Repeat step 4 until 0°+/-2°, is obtained.
Turn the ignition OFF.
Tighten the distributor hold-down bolt to 3 Nm (25 lb. ft.).
Start the engine, raise engine speed to 1000 RPM and recheck Camshaft ****** Offset.
Thank you for using fixya and good luck.

I'm with you leaning on a maf/sensor, also be sure to clean out the Idle Air control...usually hand in hand...another issue could be "bad gas" did your GMC sit for any period of time? Try adding two bottles of gas tank injector cleaner...I prefer the STP super concentrated in the black bottle...Walmart is definitely the cheapest for these bottles by 2 or 3 bucks...Hope this helps.

Check all your vacuum hoses especially at the PCV coming off the valve cover it is often over looked. The PCV fits loose either put a new bushing in the cover or add some black tape to the PCV at least until you figure out that might be the issue. Also your timing should be at TDC or 2 degrees plus or minus. Contrary to popular belief You can use a timing light you can see the timing mark know about where it is and line up the fly wheel mark accordingly.