Transmission Not Shifting?

Thank you for using 2CarPros. Com. Tell your friends, family and anyone you like about us and please return with any auto related questions, we're here to help.

Pressure washing is the enemy of today's computers. Pull connections on ECM and TCM and check for water intrusion. If it does try a hair dryer on connections then smear dielectric grease on there and see what happens. Do same at transmission as I am assuming this is an automatic transmission. Finally if it continues look for broken wires at transmission and scan for codes. Also, because it is a 4.0L check for harness hitting back stud of engine bolt and grounding out.

Hi Tom,

Here are the diagnostic procedures.

TC-179A

1. If DTCs P1745 and P1749 are set in addition to DTC P1747, repair faulty transmission case ground. If specified DTCs are not set, go to next step.

2. Using scan tool, record, then clear TCM DTCs. Raise and support vehicle. Place gearshift lever in "D" (Drive) position and accelerate to 55 MPH using light throttle. Repeat procedure 2 more times from zero MPH. If DTC P1747 resets, go to step 4). If DTC P1747 does not reset, go to next step.

3. Conditions necessary to set DTC P1747 are not present at this time. Inspect condition of related wiring and harness connectors. Repair as necessary. If no problem is found, go to DIAGNOSTIC AIDS

4. Turn ignition off. Disconnect transmission solenoid harness connector. Using a DVOM, measure resistance between ground and solenoid No. 2 control circuit (Dark Blue/White wire) at transmission side of harness. If resistance is less than 20 ohms, go to next step. If resistance is not as specified, go to step 7).

5. Disconnect TCM harness connector. Turn ignition on. Using a DVOM, measure voltage between ground and solenoid No. 2 control circuit (Orange/White wire) at TCM harness connector. If reading is greater than one volt, repair Orange/White wire for a short to power. If reading is not as specified, go to next step.

6. Turn ignition off. Using a DVOM, measure resistance of solenoid No. 2 control circuit (Orange/White wire) between transmission solenoid harness connector and TCM harness connector. If resistance is less than 5 ohms, replace TCM. If resistance is not as specified, repair open in Orange/White wire.

7. Remove transmission oil pan. Disconnect solenoid No. 2 harness connector. Using a DVOM, measure resistance between ground and terminal of solenoid No. 2. If resistance is less than 20 ohms, repair open in solenoid No. 2 control circuit (Dark Blue/White wire). If resistance is not as specified, replace solenoid No. 2.

Diagnostic Aids
Visually inspect related wiring and harness connectors. Check for broken, bent, backed-out or corroded terminal pins. Check for wires that are chafed, pierced or partially broken inside insulation. Repair as necessary. If no problems are found, refer to any Technical Service Bulletins (TSBs) that may apply.

Is the check engine light coming on?

Could be a valve body and a shift solenoid problem-have it pressure tested to find out more what's going on

Could be a bad governor as it will control downshifts and upshifts. You need a trans guy to help you. This is beyond fluid servicing.

Roy

Your welcome

May be a shift solinoid in tranny.

Hi glennbenjamin, Welcome to 2carpros and TY for the donation

Do you have a check engine light?

Check the transmission fluid level and condition if okay -bring it in and have it pressure tested this will indicate what's going on with it-could be a throttle and governor pressures are low, sticking shifting solenoid, torque converter and valve body etc

$th gear is applied electrically using an overdrive solenoid switched by the Powertrain Control Module. If the fluid smells ok and looks ok it may be electrical in nature and the torque converter or hydraulic valves may be at fault. Sorry but it must be tested with a scan tool to eliminate what is ok, and pinpoint what the problem is. If the fluid smells burnt, it will need repair or replacement. An input to the Pcm may be at fault also. Check the fluid so if it is the worst news at least you will know they are not trying to do a repair that isn't neccesary. High mileage, 16 years old so be prepared for anything. At least you will know how to make the right decision if you have it serviced by the manufacturers dealer technician. Good luck. You could just keep it out of overdrive and use it like that for a short time also but the fluid tells the story. Goodbye