5.4 transmission code after replacing intake gasket/valve cover gaskets

[71Rcode]

Hi, guys. Happy New Year from TX! Thanks in advance for your help troubleshooting.

I spent a couple of my days off under the hood of my 2001 5.4 4x4 XLT Expedition (147k on her now) replacing the intake manifold gasket (two years of cold weather-only lean codes), leaking valve cover gaskets (spark plug wells on passenger side filled with oil), thermostat, water pump, spark plugs, tensioner, idler, and serpentine belt. Lots of long stories with all of these projects and beat up hands/back, but I think I won the fight. (Hint: If you ever change the valve cover gaskets, get the gaskets WITH the grommets. Most don't come with grommets for the bolts... oil leaks past the original bolt grommets even with new gaskets. Yes.. I had to do the job twice).

All is back together and the truck is running well. However, I'm now getting a P0705 engine code (transmission range sensor) that is causing the OD light on the gear shift stalk to blink off and on with every start up.

I'm thinking this HAS to be related to the work I did pulling the intake and valve covers. I had to disconnect three wiring harness blocks/bulkheads on the passenger side (firewall; two bulkhead/harness blocks were held together with a 10mm bolt) to remove the RH valve cover. I've double checked all harnesses and all are tight and clean. Also, I'm seeing no moisture or dirt on the plugs that could be causing an issue.

Before I pull the trigger on a new transmission range sensor switch and replace that, I wanted to check with the pros on this site first. Is there a particular connection that I should recheck that may be causing the the P0705 transmission code? Perhaps something I might've removed? I tried following the wiring from the TPS to the engine compartment but can't follow it. I'm thinking it has to have routed into one of the bulkheads on the RH side of the engine compartment.

Thanks for the advice, guys.

 

[71Rcode]

Update: I just replaced the transmission range sensor with a new/aftermarket part and am getting the same PO705 code.

Hoping you guys can advise on the TRS sensor harness routing and potentially what I might've disrupted on the passenger side of the engine when disconnecting the wiring harnesses to remove the LH valve cover.

(Also, I wanted to correct my original post. I meant to state LH/passenger cover and not RH (driver's cover).

Thanks much!

 

[rjdelp7]

The Throttle Position sensor, is tied into the transmission. There may be a relearn procedure for the TPS and transmission module. Check all your connections, near the throttle. Good luck.

 

[71Rcode]

Thanks man! Good to know. I just checked the throttle position sensor and don't see anything disconnected/corroded. Could a mis-aligned throttle position sensor cause this issue with the transmission P0705 code and flickering O/D light? Or would the TPS have to be failing? (not experiencing any other trouble codes).

One thing... when I start the truck, the RPMs rev to about 1600 RPM for a couple seconds before idling down (after about 10 seconds of running). She never did that before I replaced the intake gasket. Another new behavior is idle has dropped at least 150 RPMs (idling around 650 now) when fully warm, which I had been attributing to eliminating the lean condition. So a few weird/new behaviors since I pulled the intake and valve covers.

What do you think?

 

[rjdelp7]

Try switching the ignition off and on 3 times, stopping the 3rd time on ACC/on. Then slowly depress the gas pedal to the floor and release quickly. I am pretty sure this is the TPS re-learn. Check your throttle linkage and springs.

 

[71Rcode]

Thanks again for the advice on that. Your "binding" comment got me thinking. When I was reassembling everything last week I routed the throttle and cruise cables UNDER the top radiator hose. I'd been thinking about that and if that was incorrect. I just checked a few pix I'd taken before the job and realized they should be routed OVER the top rad hose, so I just routed correctly before I headed into work. I also tried your trick of relearning the IAC 2-3x.

Unfortunately, no change. With every ignition start after the code clear, the O/D begins to flash and i'm getting the P0705.

Great ideas. Please keep them coming. Much appreciated!

 

[71Rcode]

Whoa.... update. I moved the truck tonight and decided I'd start her in neutral to see if anything changed. Well, no high initial idle and no flashing O/D or trouble code after moving in and out of gear. She ran just like she always did. I'm going to drive her around tomorrow a bit to see if there are no codes.

 

[71Rcode]

SUCCESS!!! After some very strong advice from an older / retired mechanic I know and a strong poster on the ford-trucks.com forum, I took a close (strong reading glasses) look at the 38- (black) and 36-pin (gray) connectors (I counted... not sure if the # of pins are correct) at the firewall that I had previously removed. Both of those connectors snug up with a 10mm bolt. I was looking for burnt/corroded male wire connection prongs as well as on the female plug.

I found a male connector (single wire) in the 36-pin connector had laid over (bent into an "S" shape when I originally re-attached the harness. I was able to straighten it back out and ease it back into the connector.

Problem solved. No more flashing O/D light, no more high idle upon start up, and no more P0705 code (so far).

RJDelp7, thanks for being the only one to offer advice. I appreciate you, man!

 

[71Rcode]

For anyone searching this thread for valve cover gasket replacement / intake replacement, you can do the job. One piece of advice... if you do the valve cover job, make sure to replace the rubber grommets on the valve cover bolts or the oil will leak past (yes, I had to pull the valve covers twice - second time with the intake in place --- what a beating).

I referenced these videos before tackling the job...Watched them all and took notes. Hope it helps.




RTV 20m mark

fan clutch removal

hose under intake leaking

valve cover gasket
https://www.youtube.com/watch?v=cI8pXnzdnXI&t=937s

https://www.youtube.com/watch?v=KYUJzqLqQrs