This code typically means a turbo actuator internal error code, problem unknown.
57.6.1
Actuator Check
Check as follows:
1. Check for multiple codes.
[a] If 641/9, 641/11, 641/14 or 2795/9 are present, service those faults first.
[b] If only 641/31 is present, go to the next step.
2. Disconnect the turbo actuator.
3. Turn the ignition ON (key ON, engine OFF).
4. Measure the voltage between pins 1 and 2 of the turbo actuator connector on the engine
harness side.
[a] If the voltage is less than 11.5 volts, go to the next step.
[b] If the voltage is greater than 11.5 volts, go to step 6.
5. Measure the voltage between pin 1 of the turbo actuator harness connector and ground.
[a] If the voltage is less than 11.5 volts, repair the cause of low voltage between pin 1
of the turbo actuator harness connector and pin 93 of the MCM 120–pin connector.
Refer to section 57.6.1.1.
[b] If the voltage is greater than 11.5 volts, repair the open between pin 2 of the turbo
actuator connector on the engine harness side and pin 38 of the MCM 120–pin
connector. Refer to section 57.6.1.1.
6. Turn ignition OFF.
7. Disconnect the MCM 120–pin connector.
8. Measure the resistance between pin 3 of the turbo actuator harness connector and pin 74
of the MCM 120–pin connector.
[a] If the resistance is less than 3 Ω, go to the next step.
[b] If the resistance is greater than 3 Ω, repair the harness between pin 3 of the
turbo actuator harness connector and pin 74 of the MCM 120–pin connector.
Refer to section 57.6.1.1.
9.Measure the resistance between pin 4 of the turbo actuator harness connector and pin 75
of the MCM 120–pin connector.
[a] If the resistance is less than 3 Ω, replace the turbo actuator.
[b] If the resistance is greater than 3 Ω, repair the harness between pin 4 of the
turbo actuator harness connector and pin 75 of the MCM 120–pin connector.
Refer to section 57.6.1.1.
57.6.1.1
Verify Repairs
Verify repairs as follows:
1. Turn ignition OFF.
2. Reconnect any electrical connections that were disconnected to perform the diagnosis.
3. Clear codes with DDDL 7.0 or latest version.
4. Start and bring engine up to operating temperature (over 140°F/60°C).
5. Verify operation is satisfactory and no warning lamps illuminate. If warning lamps
illuminate, troubleshoot the codes. If assistance is required, call the Detroit Diesel
Customer Support Center at 313–592–5800.
