Transmission Controls With PCM

Diagnostic Chart:

Wiring Diagram:

NO 4TH GEAR
During normal driving modes the PCM/TC adapts line pressure to prevent clutch slip and harsh shifts. If 4th clutch is slipping after pressure is adapted to high line it is determined that there is no 4th gear. Fourth gear clutch is applied by opening circuit 446 at the PCM.

DTC PARAMETERS
DTC 24 can be set while driving in 4th (steady state) or during an upshift to 4th when the PCM has detected the following conditions twice per ignition cycle.
^ Vehicle speed is above 5 km/h (3 mph).
^ Turbine speed is greater than 224 rpm.
^ No turbine or vehicle speed signal noise code.
^ High line pressure has been commanded.
^ Ratio failure counter is 255 at steady state or shift counter is greater than 100 during a downshift or upshift.

TEST DESCRIPTION
Numbered Steps below refer to numbered steps on chart.
1. Check for diagnostic trouble codes/information flags 14, 45, 46, 49, 68, 76, 77, 95, or 99. They must be eliminated first as a possible cause of DTC 24.
2. Check actuator operation. Use actuator quick check. The actuator quick test will Pulse Width Modulate (PWM) the actuators at a set rate. Listen and compare the noise of 4th gear actuator to that of other actuators. The noise of all should be similar.
3. Check pressure regulator valve operation. Use pressure test. Make sure pressure increases in correct increments during pressure test. If pressure is low, repair for pressure condition first.
4. Apply compressed air, with rubber nozzle on air gun. This step determines if there is an internal problem.
5. If there is cross leak to another clutch, there may also be another code set indicating a gear stuck on. This may help diagnose and pinpoint the source of a leak.
6. As pressure is applied and released, the clutch plates should also apply and release. Observe oil holes in clutch housing. If oil has darkened and contains clutch plate material, the clutches have probably failed.

DIAGNOSTIC AIDS
^ When the PCM detects a fault in the circuit (open, ground, short), the PCM will open the circuit internally to protect the circuit.
^ Could be a hot or cold only condition. If condition is intermittent, try to reproduce conditions in MALF table to reset the code.
^ Problem could be internal. Possible hydraulic leak in 4th or the 4th clutch is failed.