PCM interchangability
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4th Gear
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PCM interchangability
I am looking for a new PCM for my truck. I previously took it out after not being able to read codes and fuel pump always on to replace the capacitors and fix a trace. Put it back in and no change. Sent it to a PCM repair place, they did not do any repairs and said it checked out good(fuel pump turned after 2 seconds, voltage rails good). Put it back in the truck and no change in symptoms. Also of note, the truck is running extremely rich. All injectors cleaned, ignition system replaced, grounds cleaned. Any ways the PCM in the truck is SAD0 F4TF-12A650-AKA. I have only found a handful for more than a thousand bucks, I bought the whole truck for a thousand bucks so am looking for a cheaper alternative. It is a 1995 F250 7.5L 5 speed 4x4. If I find another PCM that was used for a 1995 F250 7.5L 5 speed 4x4, would that have any chance of working? Are there other causes of the PCM not working properly in the truck but working outside the truck?
This is the exact fit: https://www.ebay.com/itm/182687531239.
This is the exact fit: https://www.ebay.com/itm/182687531239.
FTE Legend
Joined: Jun 2006
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From: Ottawa, Ontario
What is the fuel pressure at idle?
Have you confirmed that the fuel pump relay isn't stuck closed? The fuel pump should not engage with the PCM removed, if it does then you have a stuck relay or a wiring short somewhere. The PO could have even bypassed the relay to make the pump run all the time.
Have you confirmed that the fuel pump relay isn't stuck closed? The fuel pump should not engage with the PCM removed, if it does then you have a stuck relay or a wiring short somewhere. The PO could have even bypassed the relay to make the pump run all the time.
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4th Gear
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Thank you for your response. The fuel pressure sits at 35psi and I can hear the regulator working. The pump is off when the PCM is removed or when the fuel pump relay is removed. As far as I can tell, the PCM is definitely commanding the pump on. I also confirmed continuity between the fuel pump control wire and the PCM connector. The only thing I have been able to think of is a wiring issue somewhere, Ive cleaned all the grounds and briefly inspected obvious connectors but haven't spotted anything. I have ordered a electrical manual from rock auto, getting shipped right now.
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4th Gear
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Oh, I hadn't seen those from Oreilly's. Thanks for pointing me that way. I had to call and they said they would have to call cardone to see if they had any available. This rarity is one of the reasons I'm looking to see if I can put a different number in there.
FTE Legend
Joined: Jun 2006
Posts: 31,930
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From: Ottawa, Ontario
So you measured the TPS to have a smooth sweep from something below 1v at closed throttle to about 4.5v at wot?
The O2 is not measurable with a multimeter unless it is a high tech version, the O2 switches rapidly between 0 and 1v when the efi system is in closed loop at 14.7:1 air-fuel ratio, that requires a tool with an oscilloscope function. If the sensor really was sitting at a steady output voltage(as measured with an O-scope) with the engine in closed loop(at operating temp) then it's either the wrong type of sensor (downstream instead of upstream) or it's dead.
The O2 is not measurable with a multimeter unless it is a high tech version, the O2 switches rapidly between 0 and 1v when the efi system is in closed loop at 14.7:1 air-fuel ratio, that requires a tool with an oscilloscope function. If the sensor really was sitting at a steady output voltage(as measured with an O-scope) with the engine in closed loop(at operating temp) then it's either the wrong type of sensor (downstream instead of upstream) or it's dead.
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Dec 1, 2006 02:13 PM
