Frustrated
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Frustrated
Ok about 4 months ago the MIL comes on and throws P0171 and P0174 codes. I cleaned the MAF and cleared the codes. About 3 weeks later MIL comes on again and throws the same 2 codes. I discover vacuum leaks on the passenger side and replaced the PCV boot, vacuum line under throttle body and the boot behind the intake, cleared codes. About 3 more weeks pass and MIL comes on and throws the same 2 codes. This time I changed the fuel filter, cleared the codes. A couple of days later the MIL comes back on this time it throws 4 codes with 2 codes pending. Here are the codes P1131, P1151, P0136 and P0156, pending codes P2271 and P2273. Truck does have occasional rough surging idle as though there is a vacuum leak, however, I cannot find anymore leaks. Any help on this would be greatly appreciated.
Lead Driver
Joined: Sep 2006
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All the codes but one are OX sensor reports.
From their discriptions, I would first look at the wire harness for burn or rub thoughs against the exhaust or some other point.
The harness comes down the passenger side rear of the motor passed the exhaust manifold.
My guess is you had two faults at the same time causing confusion.
Some of the fault reports are from both rear sensors as well as the fronts.
This makes me suspect the harness may have an issue.
When you have a long code list, it pays to read the discriptions and see if there is a general association beyond a single code or pair and seperate out what may be different and address each group seperately.
The PCM monitors for faults from a lot of sources that can be caused from the same fault either directly or indirectly, especially if intermittant, and the time it was detected, changes.
Good luck.
From their discriptions, I would first look at the wire harness for burn or rub thoughs against the exhaust or some other point.
The harness comes down the passenger side rear of the motor passed the exhaust manifold.
My guess is you had two faults at the same time causing confusion.
Some of the fault reports are from both rear sensors as well as the fronts.
This makes me suspect the harness may have an issue.
When you have a long code list, it pays to read the discriptions and see if there is a general association beyond a single code or pair and seperate out what may be different and address each group seperately.
The PCM monitors for faults from a lot of sources that can be caused from the same fault either directly or indirectly, especially if intermittant, and the time it was detected, changes.
Good luck.
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Sorry, truck is a 1998 F150, super cab, 5.4L, 4x4, 125,00 miles. I have checked all the connections and wiring harnesses associated with the O2 sensors. No water infiltration, no loose connections. As a brief update, driving to work this morning the check engine light went off. When I stopped at work, I checked with code reader and no codes were stored. Is this even possible? Aren't these codes stored until cleared? Anyway, still have the rough idle and surging.
Lead Driver
Joined: Sep 2006
Posts: 7,907
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If you moved the harrness around looking at it, you likely temporarly removed a ground fault.
The PCM will clear codes because it still monitors the faults every drive cycle to see if they clear.
As for the roughness, you still have the second issue that has not been found yet.
My guess is a code or codes will reappear at some point.
You have to address what the codes are telling when they come up.
Before my first reply, I looked up all the codes and saw they were, all but one, associated with OX sensors both front and rear suggesting a harness issue bcause there are to many different points in fault so believe it a common cause such as a harness.
Very often people will discount, and distrust codes in favor of their own thoughts instead and struggle trying to find a solution to problems they don't understand.
Good luck.
The PCM will clear codes because it still monitors the faults every drive cycle to see if they clear.
As for the roughness, you still have the second issue that has not been found yet.
My guess is a code or codes will reappear at some point.
You have to address what the codes are telling when they come up.
Before my first reply, I looked up all the codes and saw they were, all but one, associated with OX sensors both front and rear suggesting a harness issue bcause there are to many different points in fault so believe it a common cause such as a harness.
Very often people will discount, and distrust codes in favor of their own thoughts instead and struggle trying to find a solution to problems they don't understand.
Good luck.
Tuned
Joined: Jan 2008
Posts: 289
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From: Beaumont, CA
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