I just got off the phone with the Ford Dealer and was told the reason for the E.C. light was a bad PCN (a computer module "brains" for the engine. They want $516 to relace (parts and labor). Ouch! The error codes are P0155 and P0141. ANy advice out there? Any idea on what might have caused the failure. Truck is 97 F250 HD Crew 4x4. Recently had the TTB swapped out for a Dana 60. Also have a spuratic Vacuum sounding noise coming from the engine sometime accompanied with a whining sound.

Thanx
John

 

Any idea how they came to that conclusion? Both the codes are for O2 sensor heaters. I had one do the same thing a couple months ago and it was the PCM too but I've also seen bad O2s cause the same codes.

 

I am not sure...I have a relative who is a Ford salesman out of the area. He went and talked to one of the mechanics who have been there for 15 years. He told me in that 15 years he has only seen about 4 PCMs go bad. He told me it was the O2 sensors as well. I asked my Ford dealer to fax me the test results so I can send them to this other mechananic. Do you know how they came decided it was the PCM? Is there any documentation that ties those codes to the PCM. How much did it cost to replace the PCM?

Thanx

 

If they followed the pinpoint tests correctly they would have checked the wiring from the PCM to the O2s, checked the resistance of the heaters in the O2s etc. If all of that passes then the manual says to replace the PCM. I'm not sure of the cost of the PCM and since I'm in Canada the price would probably be different anyway.

 

John,

did u ever have an aftermarket chip in there? U said your engine is not runnin very good? Are there any volts at all coming from the 02 sensors? I'm assuming its a gas engine. Ask the mechanic if its any type of open loop situation? Ask the mechanic if it's goin into closed loop?

Racerguy, u just beat me to the post. I didn't see yours when I posted.

 

No aftermarket chips. Everthing related to the engine is stock (at this time..want to put a Banks exhaust system on). It is gas (460). I will ask the Mechanic the questions above when they open (8:30 Pacific). The vacuum and whinning sounds are spuratic and sometimes it seems like it is shifting at the wrong times but you could easily drive it and say there is nothing wrong with it other than the "Engine Check" light being on. For what its worth...the vacuum and whinning sounds are independent of each other. I have heard the "whining" sounds before but only when I was at altitude (~ 7000 to 8000ft). Now I am sometime hearing it at sea level.

 

Ask him if its a bad PCM then why does it run so good?

 

Yes, I will... Thats exactly what the other Mechanic told me to do.

 

When u get more info go to Ken here @ MotorHaven! You'll find him responding to threads in the Computer Tuning Forum.

 

Will do. I will post it here as well.

Thanx for the help guys.

 

The codes that were retrieved were for the O2 heaters. It will still runs fine but wont pass emissions compliance and will turn the MIL on.

 

I just got off the phone with the Mechanic who diagnosed my truck. I asked him repeatedly if the sensors were checked first. I don't think he ever really answered that question. He said something about the way "the codes repeat"? meant it had to do with the PCM not the sensor but added (wich the service rep did not mention) he needed to replace the PCM and then would have to do further diagnostics. I am concerened the PCM will be replaced when is does not need to be and the $516 is just the beginning.

 

Is that the heat sensors that monitor outside temps? When the Ford mechanic was reading my codes he mentioned the heat sensors or something that should tell the PCM or 02's to go closed loop? Looks like the 02's are in open loop due to the custom program. He did say a chip could remedy that? And me and Ken are workin on it. We'll mostly Ken. But, they hit me for a fualty PCM too. Mechanic wasn't too worried about it though. Just documented it on the receipt. Said open loop gives me more power though. I kinda understand it but didn't really believe that. Funny though he wanted too pull it and put another one in off the lot. Just need permission from somebody.

 

The O2 heaters are used to heat the O2s up so they start working quicker. The O2s dont work until they hit a certain temperature. The sooner they work the sooner the truck meets emission standards.
Until they are working the PCM is in open loop. It isnt using the readings from the O2s to decide how much fuel to inject. It just uses built in "tables", e.g. the PCM sees that the engine is cold with a heavy load on it and it's tables for that situation say that it needs to inject fuel for X milliseconds so it does, and it doesnt worry about the emissions.
Sometimes you'll have more power in open loop for that reason. The PCM just dumps in a bunch of fuel and doesnt look at the emissions.
F250_HD_Crew I mentioned the truck I had with the same problem. I was skeptical when I got to the part of the pinpoint test where it said to replace the PCM but I did and it fixed it.
The PCM is the only place that the O2 heaters have anything in common. They are seperate circuits otherwise.
Hopefully your tech followed everything through and came to the same conclusion i did.

 

Racerguy,

Would u know, or how to find out, what exactly error codes P1131 and P1151 mean? Are these for the 02 sensor heaters too? These are the codes that the mechanic documented when my SES light started goin on 2 weeks ago. Ken said that recycling the key a few times or resetting the PCM would work. So, I've been resetting the PCM. And everytime I do it it takes longer and longer for the light to come on. Last time was yesterday at lunch and it has yet to come on. Maybe third time is a charm. Although Jolene gave me an RMA# for Ken to tweak this chip, I'm gonna try resetting the PCM another time or two. Thanks you very much for explaining everything. It's just hard to get a straight answer from the dealer. And I hate to bother Ken w/ him being so busy.