Fuel injectors are typically driven directly by power transistors in the engine computer. Relays are just not fast enough to provide the fine timing control needed. There might be an individual fuse for each injector soldered to the computer board, but I haven't ever looked at one for your model, and I've never seen injectors individually fused. Before chasing that, verify that the electrical resistance of the injector coil is the same as the other injectors. The typical resistance is between 100 and 1000 Ohms. If the coil resistance differs by more than 10%, replace the injector coil (it may be easier to remove the coil from a new injector and switch it with the old one than to pull the entire injector out and replace it, if not, change the injector). Shorts in the coil that lower the resistance are sometimes a problem.
Also check the injector cable for continuity. An easy way is with an ohmmeter that can read at least 20 Megohms. First, check the resistance between the terminals on a good cable. You should read a very high resistance - this is the leakage through the transistor and any protective components, and is some number between 5 and 20 megohms. The exact number doesn't matter, as long as you see something and it is not a short circuit (less than 1 Ohm). This verifies that the test will work (if it reads over-range, either your probe tips can't reach the contacts in the connector, or the test is otherwise not valid). Next, repeat on injector 1. If it reads open circuit (over-range), check the injector cable (note: an open fuse will give the same result as a broken wire).
Backfiring can be caused by leaking valves, (compression leak test will show this), an air leak in the inlet manifold, incorrect timing. incorrect mixture or an air leak in the exhaust manifold.
Very undesirable as it can lead to engine damage.
Time to get your test gear out and find out where the damage is.
(Replacement 'computers', in some vehiles, don't normally work unless they have been reprogrammed with the rest of the system).
when you disconnected the battery you cleared all codes and your emissions[ smog/emissions need to run their cycles to be smog test ready as of now you will fail test ------https://smogcheckvacaville.com/general-motors-drive-cycle-for-smog-check/ ------------------https://repairpal.com/how-to-perform-a-basic-drive-cycle
If the headlamps on your 2001 GMC Sierra won't turn off when the truck is started, there are a few potential causes for this issue:
1. Faulty headlight switch: The headlight switch may be malfunctioning, causing it to remain in the "on" position even when the truck is started. A faulty switch can prevent the headlamps from turning off as intended.
2. Stuck relay: There could be a stuck relay in the headlamp circuitry, keeping the power to the headlamps constantly engaged. A stuck relay can cause the headlamps to remain illuminated even when the switch is off.
3. Wiring issue: There may be a wiring problem, such as a short circuit or a damaged wire, that is causing a constant supply of power to the headlamps. This can prevent the headlamps from turning off when the truck is started.
4. Daytime running lights (DRL) malfunction: If your Sierra is equipped with daytime running lights, there could be a malfunction in the DRL system. This can cause the headlamps to stay on at all times, regardless of the switch position.
To address this issue, you can try the following steps:
1. Check the headlight switch: Inspect the headlight switch for any signs of damage or wear. If the switch appears to be faulty, it may need to be replaced.
2. Check the relays: Locate the relays associated with the headlamp circuit and check if any of them are stuck or not functioning correctly. If a relay is found to be faulty, it should be replaced.
3. Inspect the wiring: Thoroughly inspect the wiring harness and connectors in the headlamp circuit for any visible damage or loose connections. If any issues are found, the wiring should be repaired or replaced as necessary.
4. DRL system troubleshooting: If your Sierra has DRLs, consult the vehicle's owner manual or a service manual to understand the DRL system's operation. Follow the troubleshooting steps outlined in the manual to diagnose and resolve any issues with the DRL system.
If you're unable to identify or resolve the problem on your own, it is advisable to consult a qualified mechanic or take your GMC Sierra to a reputable auto repair shop for further diagnosis and repair.
The jack to lift the vehicle is under the rear seats. Both seat bases, (the section you sit on) tilt forward to reveal the tyre iron and the jack. The jack is a 'bottle' style. You might need to twist the big twist nut on the side of the jack 1 or 2 turns counterclockwise to get it to come out of it's storage slot. Do this the opposite way around when putting it back as it stops the jack rattling around and annoying you.
Try this website as it shows the jacking up procedure in single steps.
https://www.carcarekiosk.com/video/2004_GMC_Envoy_SLT_4.2L_6_Cyl./jack_up_car/use_your_jack_to_raise_your_car
JustAnswerhttps://www.justanswer.com > GMC Questions
Sep 3, 2022 - It is located behind the left side of the dash. Location diagram and directions to access are attached for you. Ask Your Own GMC Question. GMC ...
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Does the engine crank over and will not run or does the starter not crank? If no crank then check the battery and connections. Make sure the vehicle is in park. Possible bad starter or dirty or loose connections. If it cranks over but will not start the spray a little starter fluid into the throttle and try starting it. If it runs, then you have a fuel delivery problem. If it does not run, then an electrical problem may exist and you will need a scanner to help find the problem.
The smart flasher (GMSF) is an automotive flasher designed to accept turn, hazard, and brake inputs. The GMSF will provide corresponding outputs to the exterior lamps and instrument panel turn signal indicator lamps. This lighting system has dedicated lamps for the turn/hazard functions and dedicated lamps for the brake function. The system incorporates the use of flash rates for diagnostics. The flash rate is a calculation of the number of flashes that occur within a 60 second period. This system uses a percentage of on-time to off-time called duty cycle. For the bulb outage condition, the indicator of the vehicle side on which the outage occurs shall assume bulb outage flash rate mode. The opposite side indicator will assume the normal flash rate mode for an input from the non bulb outage side of the vehicle. Hazard warning lamp outage will maintain a normal flash rate as long as 2 or more exterior signaling lamps are functional. During all modes of operation, the IPC will receive the same flash rates and duty cycles that the exterior lamps receive. The IPC will then control the indicators in the cluster. The vehicle operator will be provided with an audible and visual indication of the flasher operation. Below is a table with flash rates and duty cycles:
Operating Condition
Flash Rate
Duty Cycle
Normal
75 to 105 flashes per minute
45% to 55%
Turn Signal Lamp Outage
2 or 3 times faster than normal flash rate
35% to 55%
The IGN E fuse in the engine wiring harness junction block supplies Ignition positive voltage to the turn signal switch assembly. With the ignition switch in the RUN or START position, ignition positive voltage is connected through the turn signal and hazard switch assembly to the GMSF which is powered by the FLASHER fuse also in the engine wiring harness junction block and is grounded at G201. When the turn signal switch is placed in either the left or right position, the circuit is complete from the GMSF to the turn signal lamps and to ground. The GMSF then sends an on-off voltage signal to either the left or right turn signals and their instrument panel cluster (IPC) indicator. When the hazard switch is pressed, all turn signal lamps will flash including both IPC turn indicators. The front turn signals are grounded at G103 and G107. The rear turn signals are grounded at G401 and G402.
The IPC illuminates the TURN SIGNAL ON indicator in the driver information center when the IPC determines that the turn signal is active for more than 1.2 km (0.75 mile). The IPC also sends a class 2 message to the radio in order to activate the audible warning.
On vehicles equipped with the outside rear view mirror turn signal lamps, the turn signal voltage is also sent to the respective front door module. The door modules then distribute power and ground to the activated lamp.
For trailer wiring, separate turn signal circuits are connected through the GMSF to the trailer wiring harness.
Just left side front and back are not working?
It could need a new turn signal / hazard flasher module.
The low oil pressure will not affect the engine rpm. You need to find the low engine idle problem and correct it first. Could be a simple throttle body cleaning. This would clean out the idle control valve which could be the problem. Most service centers will be able to do that.
You have AWD? full time all-wheel drive.
Transfer Case Description and Operation
The Borg Warner (BW) model 4481, RPO NR3 transfer case is a one-speed, full time, all wheel drive (AWD), transfer case. The transfer case provides power to both axles, through an external planetary type differential, which has two different sets of pinion gears. The planetary differential provides a 40/60 torque split, front/rear, full time. This means both axles are constantly being driven for maximum traction in all conditions.
The transfer case external type planetary differential functions the same as a typical rear axle differential. The transfer case differential pinion gears function as the spider gears, and the sun gears function as the side gears.
The following actions occur because of the planetary differential:
• If the vehicle is on a hoist, the front propeller shaft can be rotated by hand.
• The vehicle cannot be driven if one propeller shaft is removed.
• Operating the vehicle on the hoist can damage the differential pinion gears, by over-spinning.
• Operating the vehicle with one propeller shaft removed causes over-spinning of the differential pinion gears.
The BW 4481 design of the planetary differential allows the use with the Vehicle Stability Enhancement System (VSES) vehicles. The VSES takes use of the planetary differential, by applying braking to a tire that has less traction and dividing the engine torque to the other axle.
The BW 4481 case halves are high-pressure, die-cast magnesium. Ball bearings support the input shaft, the front output shaft, and the rear output shaft. The transfer case requires DEXRON®III ATF GM P/N 12378470 (Canadian P/N 10952622), which is red in color.
This system does not have an encoder motor.
