Diagnostic Test

WARNING: This page is about a different car, the 2011 RAM Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.

CHECK FOR RELATED DTCS
1. Turn the ignition on.
2. With the scan tool, View all active DTCs.
  Are the P20BD, P20B9 and P20C1 DTCs active together?
  
  Yes
  - Go To 2.
  No
  - Go To 4.
CHECK THE (K476) DEF LINE HEATER OUTPUT CIRCUIT FOR AN OPEN/HIGH RESISTANCE

Fig 1: Checking DEF Line Heater Output Circuit For An Open/High Resistance
Courtesy of CHRYSLER LLC
1. Turn the ignition off.
2. Remove the DEF Line Heater Relay.
3. Disconnect the DEF Pressure Line Heater harness connector.
4. Measure the resistance of the (K476) DEF Line Heater Output circuit between terminal 87 of the Line Heater Relay connector and the DEF Pressure Line Heater harness connector.
  Is the resistance below 5.0 Ohms?
  
  Yes
  - Go To 3.
  No
  - Repair the (K476) DEF Line Heater Relay Output circuit for an open or high resistance. If the circuit fuse is found to be open, check the (K476) DEF Line Heater Relay Output circuit for a short to ground.
  - Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Refer to POWERTRAIN VERIFICATION TEST - 6.7L .
CHECK THE DEF LINE HEATER
1. Reconnect the DEF Pressure Line Heater harness connector.
2. Replace the DEF Line Heater Relay with a known good relay.
3. Turn the ignition on.
4. With the scan tool, Erase DTCs.
5. With the scan tool, navigate to Systems Tests and actuate the DEF Pressure Line Heater.
6. With the scan tool, View all active DTCs.
  Did the DTCs return?
  
  Yes
  - Using the wiring diagram as a guide, check the DEF Line Heater Relay control circuits for an open or short to ground.
  - Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Refer to POWERTRAIN VERIFICATION TEST - 6.7L .
  No
  - Test complete.
  - Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Refer to POWERTRAIN VERIFICATION TEST - 6.7L .
CHECK THE (K476) DEF LINE HEATER OUTPUT CIRCUIT FOR AN OPEN/HIGH RESISTANCE

Fig 2: Checking DEF Line Heater Output Circuit For An Open/High Resistance
Courtesy of CHRYSLER LLC
1. Turn the ignition off.
2. Remove the DEF Line Heater Relay.
3. Disconnect the DEF Pressure Line Heater harness connector.
4. Measure the resistance of the (K476) DEF Line Heater Output circuit between terminal 87 of the Line Heater Relay connector and the DEF Pressure Line Heater harness connector.
  Is the resistance below 5.0 Ohms?
  
  Yes
  - Go To 5.
  No
  - Repair the (K476) DEF Line Heater Relay Output circuit for an open or high resistance. If the circuit fuse is found to be open, check the (K476) DEF Line Heater Relay Output circuit for a short to ground.
  - Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Refer to POWERTRAIN VERIFICATION TEST - 6.7L .
CHECK THE (K478) DEF PRESSURE LINE HEATER RETURN CIRCUIT FOR AN OPEN/HIGH RESISTANCE

Fig 3: Checking DEF Pressure Line Heater Return Circuit For An Open/High Resistance
Courtesy of CHRYSLER LLC
1. Disconnect the DEF Dosing Control Unit C1 harness connector.
2. Measure the resistance of the (K478) DEF Pressure Line Heater Return circuit between the DEF Pressure Line Heater harness connector and the DEF Dosing Control Unit C1 harness connector.
  Is the resistance below 5.0 Ohms?
  
  Yes
  - Go To 6.
  No
  - Repair the (K478) DEF Pressure Line Heater Return circuit for an open or high resistance.
  - Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Refer to POWERTRAIN VERIFICATION TEST - 6.7L .
CHECK THE (K478) DEF PRESSURE LINE HEATER RETURN CIRCUIT FOR A SHORT TO GROUND

Fig 4: Checking The DEF Pressure Line Heater Return Circuit For A Short To Ground
Courtesy of CHRYSLER LLC
1. Measure the resistance between ground and the (K478) DEF Pressure Line Heater Return circuit at the DEF Pressure Line Heater harness connector.
  Is the resistance above 10k Ohms?
  
  Yes
  - Go To 7.
  No
  - Repair the (K478) DEF Pressure Line Heater Return circuit for a short to ground.
  - Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Refer to POWERTRAIN VERIFICATION TEST - 6.7L .
CHECK THE RESISTANCE OF THE DEF PRESSURE LINE HEATER
1. Measure the resistance across the terminals of the DEF Pressure Line Heater.
  Does the resistance measure between 5.7 Ohms and 6.9 Ohms?
  
  Yes
  - Replace the DEF Dosing Control Unit in accordance with the service information. Refer to UNIT, Diesel Exhaust Fluid Dosing Control , Removal .
  - Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Refer to POWERTRAIN VERIFICATION TEST - 6.7L .
  No
  - Replace the DEF Pressure Line in accordance with the service information. Refer to LINE, Diesel Exhaust Fluid Pressure , Removal .
  - Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Refer to POWERTRAIN VERIFICATION TEST - 6.7L .