U0106

DTC U0073, U0101 & U0106

CIRCUIT DESCRIPTION
The engine control module (ECM), the transmission control module (TCM) and the glow plug controller communicate control and diagnostic information via a controller area network (CAN) communication bus. The ECM monitors CAN operational status by expecting a constant flow of messages from the TCM and the glow plug controller. If the ECM fails to receive an expected message from the TCM or glow plug controller, DTC U0073, U0101 or U0106 will set depending on what communication is lost.

Condition for Running the DTC
U0073
- The battery voltage is between 8-16 volts.
- The ignition switch is ON.

U0101
- DTC U0073 is not set.
- The battery voltage is between 8-16 volts.
- The ignition switch is ON.

U0106
- The battery voltage is between 10-16 volts.
- The ignition switch is ON.

Condition for Setting the DTC
U0073
- The ECM detects that the CAN Bus reset counter is overrun.

U0101
- The ECM detects that the CAN Bus messages from the TCM are not being received.

U0106
- The ECM detects that the CAN Bus messages from the glow plug controller are not being received.

Action Taken When the DTC Sets
U0073 & U0106
- The ECM illuminates the malfunction indicator lamp (MIL) on the second consecutive driving cycle when the diagnostic runs and fails.
- The ECM records the operating conditions at the time the diagnostic fails. The ECM stores this information in the Freeze Frame/Failure Records on the second consecutive driving cycle when the diagnostic runs and fails.

U0101
- The ECM illuminates the MIL when the diagnostic runs and fails.
- The ECM records the operating conditions at the time the diagnostic fails. The ECM stores this information in the Freeze Frame/Failure Records.

Condition for Clearing the MIL/DTC
- The ECM turns OFF the MIL after 3 consecutive driving cycles when the diagnostic runs and does not fail. (12,000 lbs GVW)
- The ECM turns OFF the MIL when the diagnostic runs and does not fail. (Except 12,000 lbs GVW)
- A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
- A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic after the ECM turns OFF the MIL.
- Clear the MIL and the DTC with a scan tool.

Diagnostic Aids
If an intermittent condition is suspected, the following may cause an intermittent:
- Poor connections
- Misrouted harness
- Rubbed through wire insulation
- Broken wire inside the insulation

Check for the following conditions:
- Poor connection at the ECM, TCM or glow plug controller: Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.
- Damaged harness: Inspect the wiring harness for damage. If the harness appears to be OK, observe the "DTC U0073", "DTC U0101" and "DTC U0106" display on the scan tool with engine running while moving connectors and wiring harness. A change in the display will indicate the location of the fault.

NOTE: If the TCM has DTCs set, clear the DTCs in the TCM FIRST.

DTCU0073, U0101 &U0106
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Engine Controls Connector End Views or Engine Control Module (ECM) Connector End Views

Chart for 12,000 lbs GVW with A/T