Try Taking a voltage reading with a multi amp at the switch,then check the plug at the connection end to the motor. If you have a 12 volt power supply you can check the motors to see if they work ok .
For hydrolic lifters turn engine over until both valves on the cyl. your doing are completly closed, if rocker is tight after you do this loosen it until you can wiggle it and then tighten it down until you just can't wiggle it, and then give it another 1/2 to 3/4 of a turn more and thats it, repete this process on the rest of the cyl. and valves and you got it if you still have lifter or rocker noise after you do this find witch one it is and tighten it a little more . If it happens to be solid lifters you will need a feeler guage in thousands and know the setting for each valve, and its the same process except you use the guage between the rocker and top of valve to set the lash.
Good place to get a vacuum gauge hooked up and identify problems using that tool. Without the gauge, check your exhaust and see how much if passing through the converter. You can do this by testing the temperature of the exhaust before and after the converter making sure the converter/exhaust isn't restricted. As the vehicle warms up a bad converter can cause the symptoms you are describing.
2CarPros
https://www.2carpros.com > ... > Location
Dec 27, 2021 - Hello, this vehicle has two oxygen sensors, the rear one is behind the Catalytic Converter. Below is a picture of its location to the right side .
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The C0292 code in your 2004 GMC Yukon Denali XL indicates a communication issue between the Powertrain Control Module (PCM) and the Electronic Brake Control Module (EBCM). Here are some steps to diagnose and potentially fix the problem:
Check Ground Connections:
Inspect the ground connections related to the PCM and EBCM.
Follow the ECM ground and ABS module ground.
Check the ground on the firewall (driver's side) and the frame rail under the driver's seat.
Also, verify the engine ground on the driver's side.
Inspect Wiring and Connectors:
Visually examine the wiring harness and connectors associated with the EBCM.
Look for any signs of damage, such as broken wires or corroded pins.
Ensure that the connector pins are not bent or pushed out.
Pay attention to any loose or poor electrical connections.
Consider the Tune:
If you've recently modified the vehicle's tuning, consider reverting to a different tune.
Sometimes, a specific tune can cause communication issues.
If you suspect the tune, contact the tuner for further guidance1.
Professional Diagnosis:
If the above steps don't resolve the issue, it's advisable to seek professional help.
A qualified mechanic can perform a thorough diagnosis using specialized tools.
Keep in mind that diagnostic costs typically range from $75 to $150 per hour.
It is not legal to 'adjust' speedometers.
Fit the correct sized rims and tyres and the speedometer reading will be correct or use a satnav for real time speed.
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