Skip the auto shop - Our mechanics make house calls

Q: Bad pcm?

asked by on

I have a 2000 f250 5.4 2v it runs horribly I've connected a snap on scanner to the Pam and it shows no codes but the long term fuel trim on the right bank shows -25 and the left 20 I have replaced coils and plugs and gapped the plugs when I perform a koer test the codes are for right bank running rich well I can unplug all injectors on the right side and it still says rich I've replaced both o2 sensors same code I tested the injectors to see if they were stuck open they weren't I can unplug the crank position sensor and not have a code I've run the truck for long periods of time and the scanner only says obd-II system check incomplete I have run it long enough to complete a system check I need to know if my pcm is bad due to no codes and making the right bank run lean even with the injectors unplugged and there was no change in the engine

A: If you can run your engine, with the fuel i...

If you can run your engine, with the fuel injectors on the right bank disconnected, it is not your PCM (ECM). By disconnecting the injectors, the computer cannot put fuel in without opening the injectors.

You need to check the fuel pressure to see if your pressure goes up to specification and stays there after the key is off. If you have immediate leak down of pressure you need to check if the fuel injectors are stuck or leaking. If you remove the fuel injector line with the injectors attached you should see one of them leaking.

Replace the injector and then clear the codes. Monitor the short term fuel trip and you should see it start to go back to normal.

If you need assistance with this, enlist a certified mechanic who can perform the necessary checks to properly diagnose this issue and replace your fuel injectors if necessary.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Turn signal and brake light

It sounds like you may be having an issue with the wiring to the rear lights of your vehicle. I would recommend having a qualified professional inspect the wiring that controls the rear lights of your vehicle. This may include...

Q: My car tried to turn over but couldn't - it just made multiple clicking sounds then powered on after 5 seconds

Hi. This sounds like you have low voltage battery or the battery is bad and can not take a load. The battery or alternator fuse if blown would kill the power to the whole car and there would not be...

Q: signals, daytime running lights are not working, park brake light on dash is on steady and chime is dinging steady 4x4 wont engage

This is likely a brake light switch problem. I would suggest testing the brake light switch which should be located down by the brake pedal. This may also be a computer problem as well as indicated by the other lights...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...