Diagnostic Test

CHECK THE MODULE STATUS ON THE CAN C BUS
1. Turn the ignition on.
2. With the scan tool, read the CAN topology on the Vehicle View screen.
  Does the Vehicle View screen indicate that the Module is active on the bus?
  
  Yes
  - The condition or conditions that originally set this DTC are not present at this time. Using the wiring diagrams as a guide, check all related splices and connectors for signs of water intrusion, corrosion, pushed out or bent terminals, and correct terminal tension and repair as necessary. If no problems are found, test complete.
  - Perform the TRANSMISSION VERIFICATION TEST. Refer to F21-250 GEN III TRANSMISSION VERIFICATION TEST or TRANSMISSION VERIFICATION TEST - 948TE 9HP48 .
  No
  - Go To 2
CHECK THE FUSED B(+) CIRCUIT FOR AN OPEN OR SHORT TO GROUND
NOTE:
The CAN bus will remain active with the scan tool connected and the ignition off.

NOTE:
Leave the scan tool connected

and on the Vehicle View screen.
1. Turn the ignition off.
2. Disconnect the Transmission Control Module (TCM) harness connector.
3. With a 12-volt test light connected to ground, check the Fused B(+) circuit at the TCM harness connector.
  NOTE:
  The test light must illuminate brightly. Compare the brightness to that of a direct connection to the battery.
  
  Does the test light illuminate brightly?
  
  Yes
  - Go To 3
  No
  - Repair the Fused B(+) circuit for an open or short to ground.
  - Perform the TRANSMISSION VERIFICATION TEST. Refer to F21-250 GEN III TRANSMISSION VERIFICATION TEST or TRANSMISSION VERIFICATION TEST - 948TE 9HP48 .
CHECK THE FUSED IGNITION CIRCUIT FOR AN OPEN OR SHORT TO GROUND
1. Turn the ignition on.
2. With a 12-volt test light connected to ground, check the Fused Ignition circuit at the TCM harness connector.
  Does the test light illuminate brightly?
  
  Yes
  - Go To 4
  No
  - Repair the Fused Ignition circuit for an open or short to ground.
  - Perform the TRANSMISSION VERIFICATION TEST. Refer to F21-250 GEN III TRANSMISSION VERIFICATION TEST or TRANSMISSION VERIFICATION TEST - 948TE 9HP48 .
CHECK THE GROUND CIRCUIT FOR AN OPEN OR HIGH RESISTANCE
1. With a 12-volt test light connected to 12 volts, check the Ground circuit at the TCM harness connector.
  Does the test light illuminate brightly?
  
  Yes
  - Go To 5
  No
  - Repair the Ground circuit for an open or high resistance.
  - Perform the TRANSMISSION VERIFICATION TEST. Refer to F21-250 GEN III TRANSMISSION VERIFICATION TEST or TRANSMISSION VERIFICATION TEST - 948TE 9HP48 .
CHECK THE CAN C1 BUS (+) CIRCUIT FOR AN OPEN OR HIGH RESISTANCE
1. Measure the voltage between ground and the CAN C1 Bus (+) circuit at the TCM harness connector.
  Is the voltage below 2.5 volts?
  
  Yes
  - Repair the CAN C1 Bus (+) circuit for an open or high resistance.
  - Perform the TRANSMISSION VERIFICATION TEST. Refer to F21-250 GEN III TRANSMISSION VERIFICATION TEST or TRANSMISSION VERIFICATION TEST - 948TE 9HP48 .
  No
  - Go To 6
CHECK THE CAN C1 BUS (-) CIRCUIT FOR AN OPEN OR HIGH RESISTANCE
1. Measure the voltage between ground and the CAN C1 Bus (-) circuit at the TCM harness connector.
  Is the voltage below 1.3 volts?
  
  Yes
  - Repair the CAN C1 Bus (-) circuit for an open or high resistance.
  - Perform the TRANSMISSION VERIFICATION TEST. Refer to F21-250 GEN III TRANSMISSION VERIFICATION TEST or TRANSMISSION VERIFICATION TEST - 948TE 9HP48 .
  No
  - Replace and program the Transmission Control Module (TCM) in accordance with the Service Information. Refer to MODULE, TRANSMISSION CONTROL (TCM), REMOVAL AND INSTALLATION and TRANSMISSION CONTROL MODULE PROGRAMMING - 948TE .
  - Perform the TRANSMISSION VERIFICATION TEST. Refer to F21-250 GEN III TRANSMISSION VERIFICATION TEST or TRANSMISSION VERIFICATION TEST - 948TE 9HP48 .