Hi Guys,
I have a 2001 caravan with 157000 miles on it that went into limp mode last week. I didn't have a code reader so after surfing the net I read where most of the time the speed sensors were the cause. I replaced both sensors, no luck, I took the Van to the dealer and he said I have a P605 code and that the TCU was bad. I bought a rebuit module from All Computer Resources that came with my VIN data loaded and has a lifetime warrenty. The new TCU still did not resolve my problem, I feel there was a problem with the old TCU because I could not get the P0700 to reset, and I can with the new module. I borrowed a code reader and found the code I have now is P1787, OD pressure switch. I can reset the code and the Van will start in 1st and shift to 2nd and once or twice it even shifted to 3rd, but most of the time it shifts to 2nd and hangs, when it does this sometimes there are no codes set and I can shut the motor off and it will start back in 1st. Sometimes when it is in 2nd the code reader does not show it in LIMP mode, but it will eventully go into Limp and the P1787 will be set and P0700 on the dash. I pulled the plug off the solenoid pack and there is some oil in the plug, could the solenoid pack malfunction and not show a code?

Thanks in advance,
Danny

 

Symptom:
P1787-OD HYDRAULIC PRESSURE TEST FAILURE
When Monitored and Set Condition:
P1787-OD HYDRAULIC PRESSURE TEST FAILURE
When Monitored: In any forward gear with engine speed above 1000 RPM shortly after
a shift and every minute thereafter.
Set Condition: After a shift into a forward gear, with engine speed > 1000 RPM, the TCM
momentarily turns on element pressure to the clutch ckts that don’t have pressure to
identify the correct pressure sw closes. If the pressure sw does not close 2 times the code
sets
POSSIBLE CAUSES
INCORRECT FLUID LEVEL
LOSS OF PRIME DTC P1791 PRESENT
RELATED DTC’S PRESENT
INTERMITTENT WIRING AND CONNECTORS
TRANSMISSION CONTROL RELAY OUTPUT CIRCUIT OPEN
OD PRESSURE SWITCH SENSE CIRCUIT OPEN
OD PRESSURE SWITCH SENSE CIRCUIT SHORT TO GROUND
OD PRESSURE SWITCH SENSE CIRCUIT SHORT TO VOLTAGE
INTERNAL TRANSMISSION
TCM - O/D HYDRAULIC TEST FAILURE

 

Thanks Master Tech, I have checked the plugs on the TCU and the Solenoid pack, no corrosion, wiring doesn,t appear to be broken. Is it normal for oil to be in the soleniod plug, it wasn't full but there was oil in the plug. The van did shift from 1st to 2nd to 3rd a coulpe of times, but most of the time it shifts to 2nd and hangs, no codes will be set, I can stop and it will shift back to 1st sometimes, and some times when it hangs in 2nd I can shut off the engine and start back and it will start in 1st. The reader sometimes will show limp mode and no codes. Am I killing the trans by continuing to test, I have driven it to the dealer and back, about 20 miles round trip and when it went into limp mode the first time my wife was about 25 miles from home. I just drive around the block when I am testing. The reader has tests I can run and a learn mode, any suggestions would be welcomed, The old girl shifted flawlessly until last week, dealer got code 605, and told me the TCU was bad so I replaced it, I did not have access to a scanner at that time, but the P0700 on the speedometer would not reset with the old module and it will reset on the new module by removing the battery cable. Any suggestions are welcome. I do know it is impossible to troubleshoot when are not working on the van yourself.
Thanks,
Danny