PCM

DTC U1102: ASC-ECU Time-Out

CAUTION:
- If the PCM output the DTC U1102, make sure to diagnose the CAN bus line.
- Before replacing the ECU, make sure that the communication circuit is operating normally.

NOTE: When the diagnosis codes relating to the CAN communication error are output, make sure of the vehicle equipment. When the vehicle is not equipped with the system the PCM communicates to, the diagnosis code is always output. This is not abnormal.

DTC SET CONDITIONS

Check Conditions
- Battery positive voltage is 10 volts or higher.
- Engine is not cranked, or at least 3 seconds have passed since engine was cranked.

Judgement Criterion
- Unable to receive ASC-ECU signals through the CAN bus line.

COMMENT

Current Trouble
- Some of the possible causes are a harness or connector damage between the PCM and the ASC-ECU on the CAN bus line, a failure in the ASC-ECU power supply system, a failure in the ASC-ECU, or a failure in the PCM.

Past Trouble
- Proceed to troubleshoot based on a harness or connector damage on the CAN bus line between the PCM and ASC-ECU, and a failure in the ASC power supply system.

CAUTION: When the ignition key is maintained within the range "A" (i.e., the ignition switch IG2 is in OFF position but the cranking does not start) for more than 1 second, PCM stores DTC U1102 (the past trouble).

NOTE: If a malfunction occurred in the past, a failure cannot be discovered through the MB991958 CAN bus diagnosis even if there might be a problem with the CAN bus. Furthermore, it is possible to narrow down the areas of the possible failures from the DTCs that are output by the ECUs, which are communicating on the CAN bus (Refer to Explanation about The Scan Tool (M.U.T.- III) CAN Bus Diagnostics). [1][2]CAN Bus Diagnostics

TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
- CAN line harness damage or connector damage.
- ASC-ECU failed.
- PCM failed.

DIAGNOSIS

Required Special Tools:
- MB991958: Scan tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: USB Cable
- MB991910: Main Harness A

STEP 1. Using scan tool MB991958, diagnose CAN bus line.

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. Diagnose CAN bus line.
4. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the CAN bus line normal?

YES : Go to Step 2.

NO : Repair the CAN bus line. Then go to Step 6.

STEP 2. Using scan tool MB991958, read the diagnostic trouble code (DTC).

1. Turn the ignition switch to the "ON" position.
2. Read the ASC-DTC.
3. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the ASC-DTC set?

YES : Refer to Diagnosis - Diagnostic Trouble Code Chart. Diagnostic Trouble Code Descriptions

NO : Go to Step 3.

STEP 3. Using scan tool MB991958, read the diagnostic trouble code (DTC).

1. Turn the ignition switch to the "ON" position.
2. Read the combination meter-DTC.
3. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is DTC U1102 set?

YES : Go to Step 4.

NO : Go to Step 5.

STEP 4. Using scan tool MB991958, read the diagnostic trouble code (DTC).

1. Turn the ignition switch to the "ON" position.
2. After the MFI-DTC has been deleted, read the MFI-DTC again.
3. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is DTC U1102 set?

YES : Replace the ASC-ECU. Then go to Step 6.

NO : It can be assumed that this malfunction is intermittent of CAN bus line between PCM and ASC-ECU.

STEP 5. Using scan tool MB991958, read the diagnostic trouble code (DTC).

1. Turn the ignition switch to the "ON" position.
2. After the MFI-DTC has been deleted, read the MFI-DTC again.
3. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is DTC U1102 set?

YES : Replace the PCM. When the PCM is replaced, register the encrypted code. Then go to Step 6.

NO : It can be assumed that this malfunction is intermittent of CAN bus line between PCM and ASC-ECU.

STEP 6. Using scan tool MB991958, read the diagnostic trouble code (DTC).