Mechanics

WHY IS MY "SERVICE ENGIINE SOON" LIGHT IS ON?

2003 Ford F-150 • 106,000 miles

I took it to O'Reilly's and they said something about fuel mixture too rich.

Ford said it was the "heated oxygen sensor". Said they had never had one of these situations before and had to look it up in old books. And said that they would order the sensor at a cost of $269 not including this visit. So probably over $300 most likely. I waited a week with no call from Ford, so I went to NAPA.

NAPA doesn't offer to hook up to your computer.

Next, I went to Auto Zone. They hooked up and said it was the mass airflow sensor at the intake/airfilter. They sold me an $8 can of cleaner specific to the "mass airflow sensor" only. I was told to disconnect my negative battery terminal. I did both terminals and cleaned them. I took the filter out and checked it. It was practically brand new. I located and sprayed the sensor. The sensor didn't have any dirt, grass, or refuse of any kind on it, that I could see. Put it all back together after the spray evaporated.

Cranked the engine and the light was off. It stayed off for a while, then came back on after about 100 miles. I don't drive much since I'm currently unemployed from being laid off.

I bought the truck from an individual who said the light had just come on. I have had it only a couple of months and only drove it to work. No long trips, no dirt roads.

The truck didn't have an owners manual in the glovebox. I called the guy and he said if it had one it would be in the truck.

There is some digital readout display on the ceiling that does not illuminate. The guy I bought it from said it was a compass, I think. Any relationship to the "service engine soon" light?

Any

Thank You
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Tgumbyw
February 11, 2012.




Have the computer rescanned for code/s and post them if any present-
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Rasmataz
Feb 12, 2012.
This is on a printout from AutoZone: Troubleshooting PO175

OEM Brand: Domestic

Definition: Fuel trim bank two condition

Explanation: The ECM has detected a rich or lean Air/Fuel ratio condition on engine bank two.

Probable cause: 1. If bank one and two are set together suspect a fuel pressure condition or MAF snsor fault.

2. Failed HO2S21 ( Heated oxygen sensor - Bank 2 Sensor 1 )

3. Ignition misfire condition

4. Fuel injector problem

5. Engine mechanical condition

Tiny
Tgumbyw
Feb 12, 2012.
All this information and still no engine size?

Wrenchtech
Feb 12, 2012.
My truck's engine is the 4.6 litre.

Tiny
Tgumbyw
Feb 13, 2012.
My F-150 has the 4.6 Litre engine.

Tiny
Tgumbyw
Feb 16, 2012.
You're reading too rich a mixture on the driver's side only. Now you have to determine why. Could be any number of things and needs to be troubleshooted systematically.

Wrenchtech
Feb 16, 2012.
From AutoZone: The easiest and least expensive fix was to start with the cleaning of the MAS sensor. That wasn't the cure, so to troubleshoot this issue systematically, what are the next steps from here to the end?

Tiny
Tgumbyw
Feb 17, 2012.
2. Failed HO2S21 ( HEATED OXYGEN SENSOR - Bank 2 sensor 1 ) This is from the above message, which came from AutoZone's computer scanner. It doesn't sound good. FAILED, never sounds good. Judging from your experience and knowledge, does this mean that my Heated Oxygen Sensor is at fault?

Tiny
Tgumbyw
Feb 17, 2012.
Yep, that could do it. That sensort does the reporting of rich and lean.

Wrenchtech
Feb 17, 2012.
So much of the Snitcher telling lies to the computer that the engine is running lean could also be the coolant temperatue sensor locked-up in open loop mode not switching giving fuel when not needed-

Rasmataz
Feb 17, 2012.

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