DTC 81

DTC 81: Electric Pump Relay System (Open Circuit or Short Circuit)

Electric Pump Relay System Circuit:

CIRCUIT OPERATION
The electric pump relay provides power to activate the electric pump according to the signal from the AWD-ECU.

DTC SET CONDITIONS
DTC 81 is set when the coil circuit of the electric pump relay has open circuit or short circuit.

TROUBLESHOOTING HINTS (THE MOST LIKELY CAUSES FOR THIS CODE TO BE SET ARE:)
^ Malfunction of electric pump relay
^ Damaged harness and connector
^ Malfunction of the AWD-ECU

DIAGNOSIS
Required Special Tool:
^ MB991958: Scan Tool (M.U.T-III Sub Assembly)
^ MB991824: V.C.I.
^ MB991827: USB Cable
^ MB991911: Main Harness B

STEP 1. Using scan tool MB991958, check actuator test item 04: Electric Pump Drive.

CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the LOCK (OFF) position before connecting or disconnecting scan tool MB991958.





1) Connect scan tool MB991958 to the data link connector.
2) Turn the ignition switch to the ON position.
3) Set scan tool MB991958 to actuator test mode.
^ Item 04: Electric Pump Drive.
^ Operating sound of the electric pump can be heard.

4) Turn the ignition switch to the LOCK (OFF) position.
Q: Is the pump operating properly?
YES: It can be assumed that this malfunction is intermittent.
NO: Go to Step 2.

STEP 2. Check the electric pump relay.
Q: Is the check result normal?
YES: Go to Step 3.
NO: Replace the electric pump relay.

STEP 3. Measure the resistance at electric pump relay connector B-122.








Disconnect the electric pump relay connector, and measure the resistance between terminal 1 and ground.
^ The resistance should measure less than 2 ohms
Q: Is the measured resistance less than 2 ohms?
YES: Go to Step 7.
NO: Go to Step 4.

STEP 4. Check electric pump relay connector B-122 for loose, corroded or damaged terminals, or terminals pushed back in the connector.





Q: Are the connector and terminals in good condition?
YES: Go to Step 5.
NO: Repair or replace the damaged components.

STEP 5. Check the harness for open circuit to ground between electric pump relay connector B-122 terminal 1 and ground.





Q: Is the harness wire in good condition?
YES: Go to Step 6.
NO: Repair or replace the harness wire.

STEP 6. Using scan tool MB991958, check actuator test item 04: Electric Pump Drive.





CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the LOCK (OFF) position before connecting or disconnecting scan tool MB991958.

1) Connect scan tool MB991958 to the data link connector.
2) Turn the ignition switch to the ON position.
3) Set scan tool MB991958 to actuator test mode.
^ Item 04: Electric Pump Drive.
^ Operating sound of the electric pump can be heard.

4) Turn the ignition switch to the LOCK (OFF) position.
Q: Is the pump operating properly?
YES: It can be assumed that this malfunction is intermittent.
NO: Replace the AWD-ECU.

STEP 7. Check electric pump relay connector B-122 and AWD-ECU connector C-139 for loose, corroded or damaged terminals, or terminals pushed back in the connector.








Q: Are the connectors and terminals in good condition?
YES: Go to Step 8.
NO: Repair or replace the damaged components.

STEP 8. Check the harness for open circuit or short circuit to ground between electric pump relay connector B-122 terminal 2 and AWD-ECU connector C-139 terminal 16.








Q: Is the harness wire in good condition?
YES: Go to Step 6.
NO: Repair or replace the harness wire.