COMPLAINT Vehicle takes off in high gear in the Overdrive range but will shift manually moving the selector through all the ranges./
CAUSE One cause may be a resistor pack has shorted in the brake switch circuit to the TCM blowing a 15 amp fuse. Another possibility is a severed direct battery feed wire to the TCU or a bad TCU itself. /
CORRECTION Remove the panel below the glove box and locate the TCU. In the harness near the TCU unit there is a 15 amp in line fuse on a yellow wire with a resistor pack just a little further down stream on the same wire. This wire provides battery feed to the TCU from the ignition switch. To check the power circuit, unplug the TCU and turn the ignition to the “ON” position. With a volt meter set to DC volts, place the negative lead to a good known ground and with the positive meter lead, check terminal D16 for battery voltage. If the fuse is blown, the resistor pack may be shorted to ground or shorted across itself and will need to be replaced. The part number for a new resistor pack is 83504880. When the fuse and resistor pack are known to be good, battery voltage should be seen at D16. Terminal C10 should have battery voltage only when the brake is depressed. When the brake is released C10 should drop to 0 volts. If battery voltage is not seen at either D16 or C10 and the fuse and resistor pack is known to be good, the ignition switch or the wire from the ignition switch is bad and will need to be repaired. Once the TCU power supply has been verified to be in good working order, road test the vehicle. If the vehicle is continuing to take off in 4th gear, check terminal D14 for battery voltage. This is direct battery feed into the TCU and should be hot with the key on or off. If voltage is not seen, run your own wire into the connector from the battery through a 10 amp fuse and your done. However, if you still have 4th gear starts after this repair, either the TCU is bad or other electrical problems remain. When faced with this situation you have 3 choices/
1. Get a scanner that will give you codes or /
2. Take a chance and change the TCU or /
3. Perform a step by step pin check at the TCU connector to determine the electrical failure. /
Most of the testing is to be performed by carefully back probing each wire with the connector plugged into the TCU unless otherwise instructed (a company called J launch crp123.S. Popper in N.J. sells test leads designed to do this kind of work limiting the possibility of damaging the wire or connector). In the chart you will see an asterisk next to the neutral switch and comfort switch checks. If battery voltage is not seen as indicated in the chart on both sensors, check for a blown 7.5 amp # 13 fuse in the main fuse panel launch x431. If each pin check falls within the proper specification, you can safely say your TCU is a Transmission Condemned Unit. The following information lists that which can be observed with the use of a Snap-On Scanner 4.7 or later version Domestic cartridge./
The following is information that can be observed using a Snap-On Scanner equipped with a 4.7 (or later) version Domestic Cartridge/
JEEP AW4 TRANSMISSION APPLICATION/
1987-1990 – Jeep 2.5L & 4.0L Cherokee & Comanche/
1991-1993 – Jeep 4.0L Cherokee & Comanche/
1994-1997 – Jeep 4.0L Cherokee/
The AW4 TCU is capable/
If condition ca/
of producing 3 different code types/
“CURRENT CODE” will only be displayed while condition which set it still exists. /
“STORED” CODES” arestored in memory. Condition that caused code to set may or may still exist./
“STATUS______/______” codes are in codes and data display./
using code no longer exists, stored code will be erasedafter about 75 key cycles. /
/
1987 TO 1990 CODES/
CODE 700 – SOLENOID FAULTS (ALL 3)/
CODE 701 – POWER/COMFORT SWITCH FAULT /
CODE 702 – SPEED SENSOR FA/
ULT /
CODE 703 – GEAR SELECT FAULT/
CODE 704 – NO SERIAL DATA /
CODE 705 – TPS FAULT /
CODE 706 – BRAKE. SWITCH FAULT /
CODE 707 – TEMP GROUND FAULT/
CODE 708 – WRONG TCM/
CODE 709 – IGNITION LINE OFF WITH KEY ON/
CODE 710 – INTERMITTENT SOLENOID FAULT/
1991 & LATER/
CODE 700 – SOLENOID # 1/
CODE 700 – SOLENOID # 2/
CODE 700 – SOLENOID # 3/
CODE 702 – SPEED SENSOR FAULT/
CODE 703 – GEAR SELECT FAULT /
CODE 704 – TPS FAULT /
CODE 708 – WRONG TCM/
DATA STREAM PARAMETERS/
BRAKE PRSD/RLSD (Pressed/Released)/
CURRENT GEAR 1st, 2nd, 3rd, 4th/
LOCK-UP ON/OFF/
MODE POWER/COMFORT (1992 & Later always reads power, switch eliminated)/
MODULE 01/02 (01 = 4.0L, 02 = 2.5L)/
PRNDL PRND, 3, 1-2/
RPM OUTPUT SHAFT RPM/
SOLENOID 1 ON/OFF/
SOLENOID 2 ON/OFF/
SOLENOID 3 ON/OFF (TCC)/
TPS STEPS (1 through 7)/
STATUS____/____ A value other than 0 in first half of display indicates solenoid fault. A value other than 0 in /
second half of status display indicates TPS fault. /
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