Hello, leodajim -
Thanks for your note. This problem has accumulated some history since it became an issue in March when I contacted you. I'll try to summarize....
: My 2005 Tribute with 3.0 V6 Engine is running smoothly, although there has not yet been wet weather to confirm the fix. DTCs are now down to a single code and are different from the initial misfire codes. However, some questions remain.
1. Changed plugs
: I bought Motorcraft AGSF 32 plugs (later I found out these were probably wrong) at the autoparts store, per the recommended application in the store computer. I replaced the existing plugs that had around 60k miles on them. The old plugs did not look particularly bad, although some carbon was accumulating. The gaps were all within specs.
While this seemed to remedy the misfire on cold start-up problem for about a week, the problem returned and was much worse when eventually the weather turned wet and cold. When I came home after driving 100 miles in rain, the engine was barely running. AutoZone scanned my OBD and came up with the following DTC codes: P0352, P0354, P0355, B2900, U1900, C1805.
2. PCM diagnosed:
- I bought a code scanner and found the above B, U, and C codes were no longer occurring. Some of the misfiring moved to other cylinders. I checked all the plugs for ignition from the PCM and found no spark on several of them. Verifying continuity between the coil terminals and the PCM connectors, I reasoned the problem must be in the PCM.
- I found some Mazda service bulletins related to the misfire problems on 2005-6 models, with the last written in October, 2010: 01-50/10 (btw, BBB Industries has a great service - full text TSBs for free! at http://www.bbbind.com/free_tsb.html
Although I have a healthy skepticism when it comes to manufacturer recommendations for wholesale change-out of expensive parts (their incentive is more often CYA and profit-related than recommending what's best for their customers), the TSB did seem to fit my situation: "MIL with multiple Primary Circuit DTCs P0351, 352, 353, 354…. " Unfortunately, the fix recommended in the TSB was replacement of the PCM as well as all plugs and Coils on Plugs. Mazda dealer quoted $1335 for the PCM, and around $800 for the plugs and COPs, totaling around $2,200. Aftermarket sources wanted around $450 for the PCM.
3. PCM, COPs and (newly installed) plugs replaced:
- Mazda COP = AJ09-18-100 specified in the TSB crosses to Motorcraft 1L8Z12029AB, which has since been updated to 2M2Z-12029-AC.
- Dealer recommended Motorcraft plug was AGSF32WM1.
- I found a company in South Carolina (Circuit Board Medics) with a well earned BBB rating of A+ that would either repair my PCM ($300) or send me a replacement in exchange for my core ($350). Circuit Board Medics also had an arrangement with Auto Nation Ford dealership in Minnesota for a discounted price for the COPs and plugs for their customers who were getting their PCMs fixed. Circuit Board Medics explicitly required replacement of the COPs before installing the refurbished PCM in order for the warranty to be valid. My total cost for board repair and all ignition parts was about $700.
- The Ford parts people said that the Motorcraft AGSF 32 plugs the local parts store had sold me were for a Taurus and not particularly recommended for Escapes or Tributes. Given the TSB reported COP damage due RFI from mis-matched plugs, I decided not to take a chance and so purchased the AGSF32WM1 plugs.
4. More problems: Oxy Sensor and Cam Position DTCs. Engine stalled and would not crank.
- After installing the ignition related parts and going through the key-reprogramming procedure, the engine started. It ran rough at first due to EGR gasket and PCV line not being seated properly (my goofs). These problems were quickly identified and remedied and the engine ran smoothly briefly.
- Then the MIL came on and OBD listed the following codes: P0135, P0141, P0155, P0161, P0171, P0174, P0340 (oxy sensors and Cam Position Sensor malfunctions).
- After the engine ran smoothly for 10 or 15 min, I decided to take the Tribute for a test drive, codes and all. But before I got out of the garage, the engine quit and would not crank. The dash lights stayed on with the key out of the ignition. They turned off only when I disconnected the battery. When I reconnected it, the dash lights stayed off with the key back in until I moved the switch to RUN. Then they came back on again and the starter still would not crank. Again, the dash lights still would not go out until I disconnected the battery. With the battery connected and dash lights on, the code scanner reported it could not establish a link, so I had no diagnostic codes to guide me.
5. Replacement PCM was OK.
- Since the scanner was unable to communicate with the PCM, I assumed the replacement PCM had more problems than had been fixed and was likely responsible for the newly logged DTCs. After discussing my situation with Circuit Board Medics, I returned the replacement PCM to their repair shop along with my core. They reported No Fault Found and said it worked perfectly when they checked it by installing it in their test vehicle. I asked them to repair my original PCM and send it back to me, which they did, after verifying that after repair it worked properly in their test vehicle.
- After installing my repaired PCM and going through the key validation sequence, the Tribute still had the dash lights on/ no crank problem.
6. Few clues: OBD still not communicating with scanner.
- After ruling out the PCM, I had many suspects but few leads: PATS anti-theft immobilization issue? Bad grounds? Blown fuses or bad relays? Wires or components melted from catalytic overheating? (but no real evidence of actual overheating), Alternator failure? Cam Position Sensor failure? The OBD system still was not talking to my scanner.
- I spent several days gathering circuit diagrams (Autozone has posted many of the Tribute wiring diagrams on their web site) and information on the iPATS system. I looked for reports of similar symptoms on the internet, and tried to learn how all the pieces fit together.
- Using the wiring diagrams, I eventually traced the dash lights-on-with-key-out condition to the cooling fan circuits which were keeping the PCM relay energized. I also cleaned up the battery terminals, replaced several of the relays on principle (only 1 acted questionably), and cleaned up several harness ground points.
- When I took the 3 cooling fan relays (which had all tested good) out of the Battery Junction Box, the dash lights behaved normally and the Tribute started and ran smoothly, and the PCM talked to the scanner. When I disconnected the fans and replaced the relays, it again started and ran smoothly, with no sign of the lingering dash lights.
7. Back to the Present: Running well, but not sure why.
- Unfortunately, when I reconnected the fans, the Tribute started and idled well, other than a lingering P0141 trouble code. It warmed up to the point of running the fans. I wrote "unfortunately" because now I do not have a root cause to point to. I cannot say what might have caused or what "fixed" the dash lights-on-with-key-out condition.
Here are some final thoughts (though no firm conclusions) on what I discovered through my efforts:
- The original PCM was likely damaged during my 100 mile trip in the rain. (Though I have not discussed the repair findings on my original core with the PCM repair shop.)
- I've read one or two accounts of Tributes with the misfire problem being repaired and running well for a few days and then the problem recurring. I believe the misfire problem has been addressed in the case of my Tribute as well as possible and think (hope) it will not recur.
- The larger uncertainty has to do with the dash lights-on-with-key-out/no-start condition. Although I changed out some relays and cleaned and tightened a number of grounds, I'm not sure the root problem has been fixed or that it will not reappear.
- The remaining oxygen sensor DTC P0141 may be the result of damage during the drive in the rain. My next step will be to get under the car and physically check out the wires and sensor. This seems like a more manageable problem than the misfire and the dash light/no-start condition.
If you're interested in any further details, I'll be glad to provide them.