Ok I was getting P0358 ignition coil H which i believed was cylinder8. I flipped the coil with cylinder7 now im getting code P0351 ignition coil A. Im still not exactly sure what those letters A & H stand for but i think the P0351 is cylinder1 and P0358 Is cylinder8. Am i right or wrong on that? Basically i Know i have a bad coil just trying to pinpoint it right now. 3.9Liter engine....

https://www.yourmechanic.com/article/p0358-obd-ii-trouble-code-ignition-coil-h-primary-secondary-circuit-malfunction-by-valerie

https://www.obd-codes.com/p0358

https://repairpal.com/obd-ii-code-p0358-ignition-coil-h-primary-secondary-circuit

From a reputable repair website:


P0351 - OBD-II Trouble Code

Auto Systems and Repair

Ignition Coil "A" Circuit Primary/Secondary Malfunction Our emissions expert has put together the following information about the P0351 fault code. We have also included diagnostic procedures you can take to your repair shop if the mechanic is having difficulty analyzing the code.
OBD II Fault Code

• OBD II P0351 Ignition Coil "A" Circuit Primary/Secondary Malfunction

What does this mean? The ignition coil or coils are responsible for igniting the air/fuel mixture inside the combustion chambers. Without reliable performance from the ignition coil(s) the vehicle will stumble and misfire.
Code P0351 indicates there's an electrical problem in either the primary ( the computer side ) or the secondary ( the spark plug side ) of the Ignition Coil "A" Circuit.
Symptoms

• Check Engine Light will illuminate
• Engine idles rough
• Engine misfires on acceleration
• In rare cases, the engine may not exhibit noticeable symptoms

Common Problems That Trigger the P0351 Code

• Defective Ignition Coil(s)
• Defective Spark Plug(s)
• Intake Manifold Vacuum leaks
• Carbon buildup in the Throttle Body air passages
• Defective Idle Air Control Valve or Electronic Body

Common Misdiagnosis

• Ignition coil(s) replaced when cause of the malfunction was a vacuum leak
• Spark Plugs replaced when cause of the malfunction was a vacuum leak

Same as Ford Escape.
P0351 - Ignition Coil A - Primary/Secondary Circuit

Cylinder #1, Pin 26 at the PCM, computer.

I would replace the coil on the plug (COP) for that cylinder and see if its' ok. If not, then it is possible that the bad coil took out the driver in the PCM. The test at Pin 26 to see if the light blinks, must be done with the correct tester or it will damage the PCM.

Hope it's the coil.

report results.

4 cylinder or 6 cylinder engine?

P0351 is Ignition Coil A Primary/Secondary Circuit Malfunction.
Possible causes: - Open or short in the ignition coil circuit - Ignition coil circuit shorted to ground - Ignition coil connector - Damaged ignition coil - Damaged PCM or
Possible solution - If damage, repair ignition coil circuit - Replaced ignition coil - Replaced PCM or ECM When is the code detected? The test fails when the Powertrain Control Module (PCM) or Electronic Control Module(ECM) does not receive a valid pulse signal from the ignition coil.
P0351 Description: The ignition signal from the Powertrain Control Module (PCM) or Electronic Control Module(ECM) is sent to and amplified by the power transistor. The power transistor turns ON and OFF the ignition coil primary circuit. This ON/OFF operation induces the proper high voltage in the coil secondary circuit.
Hope this helps :)

Spark plugs are not your problem

There are no letters on an LS cylinder
codes.

You won't likely have two bad COP Coils
and maybe not the #3 or#7

If not, you have to walk a new coil to find the
bad cylinder

P1391 - Not a valid obd code.
B1391 - Oil Level Switch Circuit Failure
C1391 - Not a valid obd code.
U1391 - Not a valid obd code.
Its possible you may have misread this code. If it is B1391 that would be the only code with 1391 for your vehicle.

P0351 - Ignition Coil A Primary / Secondary Circuit Malfunction. The ignition signal from the Powertrain Control Module or Electronic Control Module is sent to and amplified by the power transistor. The power transistor turns ON and OFF the ignition coil primary circuit. This ON/OFF operation induces the proper high voltage in the coil secondary circuit.

Possible Causes:
- Open or short in the ignition coil circuit
- Ignition coil circuit shorted to ground
- Ignition coil connector
- Damaged ignition coil
- Damaged PCM

P0352 - Ignition Coil B Primary / Secondary Circuit Malfunction.
Same repair info as P0351.

P0353 - Ignition Coil C Primary / Secondary Circuit Malfunction.
Same repair info as P0351



Solutions:
- If damage, repair ignition coil circuit
- Replaced ignition coil
- Replaced PCM or ECM

These codes are for a malfunctioning ignition coil/s.
P0351= ignition coil A primary/secondary circuit malfunction.
P0354= ignition coil D primary/secondary circuit malfunction.
visually check the coil packs for burn marks, damage, loose wire connectors, and the wire harness to each of the coils for damage. How long has this been happening? Has any work been done recently? Did the engine compartment recently get wet?

Have your ignition coils replaced

Hi...
On your HUMMER . the CODE P0358. refer to Electrical problem.
Or malfuntion of the ignition coil. cylinder # 7.. The last one in Driver side. Start from Front to Back. The firing order is: Driver side, 1,3,5,7,. Passanger Side 2,4,6,8.
Primary circuit. Is the Spark Plug Wire.
Secondary circuit. Is the Electrical connector on the Ignition Coil.

Check the condition of the Spark plug, Spark plug Wires. and ignition coil. and the ignition coil Electrical connector.

OK.. I hope this help on your problem.
Thank you for use fixya.