I have a 1997 F250 HD 4X4 with a 5.8L engine and E4OD transmission. The transmission seems to shift from 1 to 3 or maybe overdrive at a very low speed and then right back to 1 it will keep doing this until probably 35 - 40 mph. It has a 633 and a 622 code. The transfer case switch checks good. If I check the harness from the connector that goes to the transfer case switch (LB/bk wire) It has continuity to ground. I unplugged the plug on the left inner fender and no longer have continuity to ground. When I check continuity from the plug on the inner fender towards the PCM I have continuity to ground .When I unplug the harness from the PCM I no longer have continuity to ground. If I put my ohm meter on the PCM pin that the LB/BK wire goes to with the harness unplugged I have continuity to ground. should this pin have continuity to ground ? I would appreciate any help I can get

 

Perhaps tell us what the codes mean?

 

622 is Solenoid/circuit failure – shift solenoid 2. 633 is 4x4L switch should be in 4×2 or 4×4 high for the test.

 

Is it safe to assume that after using the search function to look up those codes then reading the other threads you did not get the help you needed? In one thread a new/reman PCM was the solution.

It sure would be nice for people to include the code descriptions in their posts instead of forcing us to go look it up.

 

[QUOTE=Mark Kovalsky;21720404]622 is Solenoid/circuit failure – shift solenoid 2. 633 is 4x4L switch should be in 4×2 or 4×4 high for the test.[/QUOTE

Code 633 transfer case in low range
I checked the transfer case switch in 2 high and 4 low with the harness unplugged the switch was working and not shorted to ground. when I checked the Light blue wire with the black stripe at the plug that plugs in to the switch I had continuity to ground. I unhooked the plug on the inner fender by the fuse box and checked at the plug the goes to the transfer case again this time it did not have continuity to ground. I checked the light blue wire with black stripe at the harness from the inner fender to the PCM at the plug on the inner fender it had continuity to ground. I unhooked the plug on the PCM and no longer had continuity to ground. plugged the harness back to the PCM and and it had continuity to ground . When I checked the pin on the PCM that wire goes to it had continuity to ground. Should that pin have continuity to ground

Code 622 solenoid circuit failure #2 solenoid

I took the plug off the transmission and checked the the solenoids with an ohm meter. they were all 20 ohms the information I had said they should have been 20-30 ohms. I checked the continuity of the solenoids at the connector on top of the inner fender and at the PCM connecter also and still 20 ohms

 

I don't know where the search function is. I read a lot different posts. I saw several with shifting problems. I didn't see the on the had a new or reman PCM. I will go look for it. I was suspecting the PCM because of the pin for the wire that goes to the transfer case switch. I was hoping someone would know if that pin was supposed to have continuity to ground. I'm older an not as good with a computer as most of the other guy's on here.

Thanks for the help

 

Right here …

 

With the PCM disconnected, check SS2 circuit for continuity to ground and to power.

 

Mark, did you mean for me to check the continuity between the two wires on the PCM connector the one that supplies the power and the one that grounds the solenoid? If so it has 21.0 ohms and no continuity from either of those wires to ground

 

No, check the continuity to the positive battery connection and the negative battery connection. With the harness unplugged on both ends, it should have no continuity to either.

 

With the plug on the transmission removed and the connector on the PCM removed I have no continuity to the power or the ground for either wire for the #2 solenoid

 

Do you have any other ideas?

 

And there is the conundrum about Code 633. The computer is expecting a High (+12VDC when the TC shifter is in Hi range) or a Low (ground when the TC is in Low range). If that signal is neither, then Code 633 is flagged.

Not correct as stated above.


That is a good start to troubleshooting Code 633



Was the transfer case shifter in the Low range position?



Is there continuity to the battery positive? It may not Key Off.




Was the transfer case shifter in the Low range position?




I do not believe that is a good sign.


No


I recall a similar Code 633 issue in recent past. Based on the EVTM diagrams the transfer case High versus Low range circuit is supplied battery power for the High and a ground for the Low signal. I believe the OP had a 2wd truck so there is nothing in the circuit to supply a low, but the High (based on the EVTM diagrams) is supposed to be coming from Fuse 17 via a steering diode to that Light Blue/Black wire. After some testing it came down to a bad PCM, with a strange failure mode.

In your case it appears you are measuring an internal ground on PCM Pin 12. That would would not trigger Code 633 IMHO, but it should cause a modified shift schedule since the PCM thinks the transfer case in Low range.

 

I don't get why the PCM needs to know if the xfer case is in high or low? It is already deciding when to shift based on speed & load, why can't it just do that?

 

In low range the PCM lowers the shift points significantly in my experience when you have an E4OD or 4R70W transmission.