Transmission trouble codes after DPFE replacement

This past Tuesday I replaced the DPFE sensor due to a P1401 trouble code and cleared the trouble code out of the PCM. The new DPFE cleaned up the idle and intermitting stalling problems. I had a high idle problem though, 950 to 1100 rpm. I drove the truck hoping it would settle down and the computer would "learn" the new sensor. During this time, my GF admitted that her brother screwed with the throttle plate stop screw. He thought it was an idle adjustment screw. I didn't have time to go through the procedure to reset the throttle plate screw properly due to some family issues.



Friday, on my way to lunch the truck started shifting hard. Eventually, the O/D light started flashing and the check engine light came on. The truck would start from a stop in second gear, shift hard into third and stay there until I came to a complete stop. Then it would start all over. I've searched and read that some people have had similar issues and after shutting down the truck for awhile then restarting it seems to go away. That's not my case. I scanned the PCM and got these codes,



P1401 DPFE sensor circuit high voltage detected



P0133 (h2os-11) circuit slow response


P0141 (ho2shtr12) heater circuit malfunction


P0732 transmission gear incorrect ratio


P1756 solenoid (shift(b))-open or short


I replaced both O2 sensors less than 10,000 miles ago and the DPFE sensor less than 75 miles ago. I also cleaned the VSS connection less than 6000 miles ago due to erratic shifting. Could all these random issues indicate a bad or failing PCM? I find it hard to believe that this truck went from needing a DPFE sensor to having this many issues and codes after the sensor replacment. The truck has close to 260,000 miles on it now. I've maintained it in top condition. I did the maintenance on it when my GF owned the truck.

All of those codes relate to electrical issues obviously and all of those systems wiring comes together near the dpfe sensor... So highly suspicious circumstance.

My first step would be to check the harness near the dpfe sensor as well as the ground strap at the firewall and pcm connection itself. Also hard reset the pcm (disconnect the battery and hold the terminals together for 10 or so mins).

Dirtman said:

All of those codes relate to electrical issues obviously and all of those systems wiring comes together near the dpfe sensor... So highly suspicious circumstance.

My first step would be to check the harness near the dpfe sensor as well as the ground strap at the firewall and pcm connection itself. Also hard reset the pcm (disconnect the battery and hold the terminals together for 10 or so mins).

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You're right. I have cleaned several connections under the truck over the past few years. I will clean those and do the reset and see what happens. Just gotta let all this rain move out first. No shop currently to work in.

Check/replace Fuse #41(20amp) in the engine fuse box

RonD said:

Check/replace Fuse #41(20amp) in the engine fuse box

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Can you elaborate on why and what fuze that is for? I don't have my manual handy to see what fuse that covers. TIA

O2 heaters, trans sensors, solenoids, a few other things

RonD said:

O2 heaters, trans sensors, solenoids, a few other things

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Depending on the weather tomorrow, I am going to try and make some headway cleaning connections and swapping out that fuse you mention. Can't hurt to try. I have a few dozen of fuses laying around just waiting for their chance to blow.

I went through all the connectors, grounds, and fuses. I cleaned and wiped everything down. I found no corrosion anywhere but cleaned everything anyway. I changed the #41 underhood fuse. Mine was a 10A mini fuse. I've never had a blown fuse in this truck, neither has my GF. I think it's all coincidental that these problems cropped up right after the DPFE change. The transmission in this truck has never shifted properly since it was bought slightly used with less than 50k miles. The truck now has just about 250K miles. I think it's time for the junkyard.