PCM Troubleshooting
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PCM Troubleshooting
I have a 92 F350 with 460 and E4OD tranny, cancel button on the shift lever. The transmission shifts fine in 1, 2, & 3 but I do not have any overdrive. When I press the cancel button I get nothing. It seems like I have no power to the cancel button. No lights, I have checked all the fuses and they tested fine. Not sure where to begin troubleshooting the PCM. Truck has a new ECM in it so I know it is not that.
Kevin
Kevin
Frmr Ford Trans Engr
Joined: Aug 1999
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From: SE Florida
Originally Posted by 2ktrott
Not sure where to begin troubleshooting the PCM. Truck has a new ECM in it so I know it is not that.
Take the plastic cover off of the steering column. Inspect the wires where they enter the shifter handle. It's common for them to fray or break there. That is probably why the button is not working.
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Mark,
I will pull the steering column plastic and inspect the wires. I was unter the impression that in the early 90's Ford made the transition to the E4OD and added a transmission control module or PCM and it received input from the ECM. So what you are saying is that since I have already replaced the truck computer and the transmission shifts fine in 1 - 3, my issue is probably electical. I will inspect as recommend and let you know how I make out. Can I test voltage on these wires?? Thanks
Kevin
I will pull the steering column plastic and inspect the wires. I was unter the impression that in the early 90's Ford made the transition to the E4OD and added a transmission control module or PCM and it received input from the ECM. So what you are saying is that since I have already replaced the truck computer and the transmission shifts fine in 1 - 3, my issue is probably electical. I will inspect as recommend and let you know how I make out. Can I test voltage on these wires?? Thanks
Kevin
Frmr Ford Trans Engr
Joined: Aug 1999
Posts: 24,732
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From: SE Florida
Ford made the transition to the E4OD starting in 1988. On IDI diesels there was a separate trans controller because there wasn't a PCM for the engine. All other engines used a PCM for both engine and transmission.
Usually you can see where the wires are damaged. One will have +12V all the time. Another, going to the lamp, will only have +12V when the OD is off. If the button doesn't work this wire will never have power.
Usually you can see where the wires are damaged. One will have +12V all the time. Another, going to the lamp, will only have +12V when the OD is off. If the button doesn't work this wire will never have power.
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Mark,
I pulled the coumn last night and found 3 wires coming out the base of the gear selector. Surprisingly all the wires looked good. I pulled the connector and metered across the wires and when I tested the outer wires and pressed the button the OD "Off" lite up. Then I jumped the middle and right the OD light "Off" lite up. However, I did not check for the presence of voltage on the PCM side of the connector. How does the switch come out and if it was bad would it hold the tranny out of overdrive. Can you give a quick explanation on how this works. From what I can gather 12volts feeds through the switch on 1 leg and when the button is pressed it switches legs and as a result signals the PCM that OD is turned off. Where does the 12v originate, the PCM or the fuse panel? Thanks for the help.
Kevin
I pulled the coumn last night and found 3 wires coming out the base of the gear selector. Surprisingly all the wires looked good. I pulled the connector and metered across the wires and when I tested the outer wires and pressed the button the OD "Off" lite up. Then I jumped the middle and right the OD light "Off" lite up. However, I did not check for the presence of voltage on the PCM side of the connector. How does the switch come out and if it was bad would it hold the tranny out of overdrive. Can you give a quick explanation on how this works. From what I can gather 12volts feeds through the switch on 1 leg and when the button is pressed it switches legs and as a result signals the PCM that OD is turned off. Where does the 12v originate, the PCM or the fuse panel? Thanks for the help.
Kevin
Frmr Ford Trans Engr
Joined: Aug 1999
Posts: 24,732
Likes: 2,661
From: SE Florida
I'm not sure where the 12V comes from. The switch is a momentary contact. When it completes the circuit to the third wire the switch from 0V to 12V tells the PCM to turn off OD. The PCM sends 12V to the light when it turns off the OD.
The switch unsnaps from the end of the shifter.
The switch unsnaps from the end of the shifter.
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