Automatic Transmission - MU5: Overview — Automatic Transmission - MU5 — Automatic Trans

Test Description

The numbers below refer to the step numbers on the diagnostic table.

This step determines if the Scan Tool is receiving power through the DLC connector.
The MIL should illuminate whenever the ignition is ON and the engine is not running.
This step determines if the PCM is transmitting serial data to the DLC and that the data circuit is not open or shorted.
This step determines if a DTC is current or stored in history.

Step	Action	Yes	No
1	Install a Scan Tool . Turn ON the ignition, with the engine OFF. Does the Scan Tool turn ON?	Go to Step 2	Go to SCAN TOOL DOES NOT POWER UP in Data Link Communications
2	Is the MIL ON?	Go to Step 3	Go to SYMPTOMS INSTRUMENT PANEL, GAGES AND CONSOLE in Instrument Panel, Gages, and Console
3	Attempt to establish communication with the PCM controller modules. Does the Scan Tool communicate with the PCM control modules?	Go to Step 4	Go to SCAN TOOL DOES NOT COMMUNICATE WITH VCM/PCM in Data Link Communications
4	Use the Scan Tool Capture Info function in order to save or capture/Store Info any DTC Information. Are there any DTCs present?	Go to Diagnostic Trouble Code (DTC) List/Type DIAGNOSTIC TROUBLE CODE (DTC) LIST/TYPE	Go to Overdrive Off Indicator Always On OVERDRIVE OFF INDICATOR ALWAYS ON

AUTOMATIC TRANSMISSION - POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK

The numbers below refer to the step numbers in the diagnostic table.

6. This step checks the VSS sensor for a battery positive supply.
7. This step checks the VSS sensor for a ground supply.
8. This step checks for a shorted to ground speedometer vehicle speed input circuit.
9. This step checks the VSS for an output signal.
10. This step checks the PCM vehicle speed input circuit for continuity to the speedometer.
11. This step checks the speedometer for an output signal. Each 1 Hz of frequency is approximately equal to one mile per hour.

The numbers below refers to the step numbers on the diagnostic table.

3. This step attempts to repeat the condition that set the DTC.
6. This step tests the circuit for an open or high resistance.
7. This step tests the circuit for a short to ground.

The numbers below refers to the step numbers on the diagnostic table.

3. This step attempts to repeat the condition that set the DTC.
6. This step tests the circuit for an open or high resistance.
7. This step tests the circuit for a short to ground.

The numbers below refer to the step numbers on the diagnostic table.

1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
3. This step checks for proper shift points.
5. This step checks for a leaky shift solenoid #1.
6. This step checks for a stuck closed shift solenoid #1.
8. This step checks the condition of the valve body assembly.
9. This step checks for a faulty PCM.

The numbers below refer to the step numbers on the diagnostic table.

The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
This step inspects the shift solenoid internal coil resistance.
This step inspects for a short to ground in the shift solenoid #1 control circuit.
This step inspects for an open in the shift solenoid #1 control circuit.
This step inspects the transaxle internal electrical harness for damage.
This step inspects for a short to voltage in the shift solenoid #1 control circuit.
This step inspects for a poor electrical connection that may have caused DTC to set.
This step inspects for a faulty PCM.

The numbers below refer to the step numbers on the diagnostic table.

1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
3. This step checks for proper shift points.
5. This step checks for a leaky shift solenoid #2.
6. This step checks for a stuck closed shift solenoid #2.
8. This step checks the condition of the valve body assembly.
9. This step checks for a faulty PCM.

The numbers below refer to the step numbers on the diagnostic table.

The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
This step inspects the internal coil resistance of the shift solenoid.
This step inspects for a short to ground in BLU wire.
This step inspects for an open in the BLU wire.
This step inspects the condition of the transaxle internal electrical harness for damage.
This step inspects for a short to voltage in the BLU wire.
This step inspects for a poor electrical connection that may have caused the DTC to set.
This step inspects for a faulty PCM.

The numbers below refer to the step numbers on the diagnostic table.

1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
4. This step checks for proper shift points.
5. This step checks for a stuck closed lock-up solenoid.
6. This step checks for a leaky lock-up solenoid.
7. his step checks the condition of the valve body assembly.
8. This step checks for a faulty PCM.

The numbers below refer to the step numbers on the diagnostic table.

The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
This step tests the shift solenoid for internal coil resistance.
This step tests for a short to ground in the BLU/WHT wire.
This step tests for a open in the BLU/WHT wire.
This step tests the condition of the transaxle internal electrical harness for damage.
This step tests for a short to voltage in the BLU/WHT wire.
This step tests for a poor electrical connection that may have caused the DTC to set.
This step inspects for a faulty PCM.

The numbers below refer to the step numbers in the diagnostic table.

1. The OBD System Check prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
3. This step will determine if the fault is in the stop lamp switch.
4. This step will determine whether there is a short to voltage in the stop lamp circuit between the PCM and the stop lamp switch.
6. This step will determine whether there is a short to voltage within the PCM, or a short to voltage in the circuit between the PCM and the stop lamp switch.

The numbers below refer to the step numbers in the diagnostic table.

2. This step checks the ISS for an output signal.
4. This step checks the ISS sensor resistance.
5. This step checks the wiring from the sensor to the PCM connector.

The numbers below refer to the step numbers on the diagnostic table.

1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
5. This step checks for a faulty PCM.
6. This step checks for a faulty solenoid.

The numbers below refer to the step numbers on the diagnostic table.

The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
This step checks the L position signal circuit.
This step checks the N and the P position signal circuit.
This step checks the P position signal circuit.
This step checks the R position signal circuit.
This step checks for poor terminal contact at the PCM.
This step checks for a faulty PCM.
This step checks for a short to voltage in the L position.
This step checks for a short to ground in the L position.
This step checks for an open in the L position.
This step checks for a short to voltage in the N and P positions.
This step checks for a short to ground in N and P positions.
This step checks for an open in N and P positions.
This step checks for a short to voltage in the 2 position.
This step checks for a short to ground in the 2 position.
This step checks for an open in the 2 position.
This step checks for a short to voltage in R position.
This step checks for a short to ground in R position.
This step checks for an open in R position.

The numbers below refer to the step numbers on the diagnostic table.

1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
3. This step inspects the condition of the solenoid and the internal electrical harness for damage.
4. This step inspects for an open or short in the 2ND brake control circuit.

The numbers below refer to the step numbers on the diagnostic table.

1.The Powertrain OBD System Check prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
2. This step checks for a short to ground in the O/D OFF indicator circuit.
3. This step checks whether the condition is caused by a short to ground or a constantly closed Overdrive switch and not due to a faulty PCM.
4. This step checks whether the condition is caused by a short to ground in the O/D OFF switch signal circuit and not due to a faulty Overdrive switch.
9. This step checks whether the condition is caused by a short to ground in the O/D OFF switch signal circuit and not due to a faulty Overdrive switch.

The numbers below refer to the step numbers on the diagnostic table.

The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
This step checks the O/D OFF indicator light by jumping the switch to ground.
This step checks the ground circuit and the Overdrive switch.
This step checks for an open LT GRN wire or an open indicator bulb.

Transmission General Description

The MU6 is a fully automatic front wheel drive electronically controlled transmission. The PCM controls shift points by means of two shift solenoids. A third solenoid controls the application of the Torque Converter Clutch. The PCM regulates oil pressure by means of a pressure control solenoid valve. A fifth solenoid controls the application timing of the O/D and 2nd brake which reduces shift shock.

You can operate the transmission in any one of the following seven modes

P - Park position prevents the vehicle from rolling either forward or backward. For safety reasons, use the parking brake in addition to the park position.
R - Reverse allows the vehicle to be operated in a rearward direction.
N - Neutral allows the engine to be started and operated while driving the vehicle. If necessary, you may select this position in order to restart the engine with the vehicle moving.
Overdrive - Overdrive is used for all normal driving conditions. Overdrive provides a fourth gear ratio which can be engaged or disengaged manually. Depress the accelerator in order to downshift for safe passing.
D - Drive position is used for city traffic and hilly terrain. Drive provides three gear ranges and drive range prevents the transmission from operating in Overdrive. Depress the accelerator in order to downshift.
2 - Manual Second provides two gear ratios under most operating conditions. Manual Second provides acceleration and engine braking. Select this range at any vehicle speed, but the transmission will not downshift into Second gear until the vehicle speed drops below approximately 96 km/h (60 mph)
1 - Manual LO provides maximum engine braking. You may also select this range at any vehicle speed, but the transmission will not downshift into First gear until the vehicle speed drops below approximately 48 km/h (30 mph).