Heating and Air Conditioning

DTC U1100: ECM or PCM time-out (related to engine)
DTC U1101: ECM or PCM time-out (related to transaxle)

CAUTION:
- If DTC U1100 or U1101 is set in the ETACS-ECU, always diagnose the CAN main bus line.
- Whenever the ECU is replaced, ensure that the communication circuit is normal.

TROUBLE JUDGMENT

DTC U1100
- The ETACS-ECU receives engine control system-related signal from the ECM or PCM . If the ECU cannot receive the signal, DTC U1100 will be set.

DTC U1101
- The ETACS-ECU receives transaxle control system-related signal from the ECM or PCM . If transaxle control system-related signal cannot be received, DTC U1101 will be set.

TECHNICAL DESCRIPTION (COMMENT)

Current trouble
- Connector(s) or wiring harness in the CAN bus lines between the ECM or PCM and the ETACS-ECU, the power supply system to the ECM or PCM , the ECM or PCM itself, or the ETACS-ECU may be defective.

Past trouble
- If DTC U1100 or U1101 is stored as a past trouble, carry out diagnosis with particular emphasis on wiring and connector(s) in the CAN bus line between the ETACS-ECU and the ECM or PCM , and the power supply system to the ECM or PCM . For diagnosis procedures, refer to "How to cope with past trouble" (Refer to How to treat past trouble).

NOTE: You cannot find a past trouble, by the M.U.T.-III CAN bus diagnostics even if there is a failure in CAN bus lines. In this case, Refer to How to Cope with Intermittent Malfunction and check the CAN bus lines. You can narrow down the possible cause of the trouble by referring to the DTC, which is set regarding the CAN communication-linked ECUs (Refer to Information Bus, CAN Bus Line Diagnostic Flow).

TROUBLESHOOTING HINTS
- The wiring harness or connectors may have loose, corroded, or damaged terminals, or terminals pushed back in the connector.
- The ECM or PCM may be defective.
- The ETACS-ECU may be defective.

DIAGNOSIS

Required Special Tools:
- MB991223: Harness Set
- MB992006: Extra Fine Probe
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-III Main Harness A

STEP 1. Using scan tool MB991958, diagnose the 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. Refer to "How to connect SWS monitor."
2. Turn the ignition switch to the "ON" position.
3. Diagnose the CAN bus line.
4. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the CAN bus line found to be normal?

YES: Go to Step 2.

NO: Repair the CAN bus line (Refer to Information Bus, Diagnosis).

STEP 2. Using scan tool MB991958, read the ECM or PCM diagnostic trouble code.

Check whether engine and transaxle DTCs are set or not.
1. Turn the ignition switch to the "ON" position.
2. Check for engine and transaxle DTCs.
3. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the DTC set?

YES: Diagnose the ECM or PCM (Refer to MFI Diagnosis in Computer and Control Systems or Diagnosis in Automatic Transmission/Transaxle).

NO: Go to Step 3.

STEP 3. Using scan tool MB991958, read the for any diagnostic trouble code.

Check if a DTC, which relates to CAN communication-linked systems below, is set.
- Combination meter
DTC indicating a time-out error related to the engine or automatic transaxle control system

- A/C
DTC indicating a time-out error related to the engine or automatic transaxle control system

1. Turn the ignition switch to the "ON" position.
2. Check for a DTC related to the relevant system.
3. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the DTC set?

YES: Go to Step 4.

NO: Go to Step 5.

STEP 4. Recheck for diagnostic trouble code.

Check again if the DTC is set.
1. Turn the ignition switch to the "ON" position.
2. Check if the DTC is set.
3. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the DTC set?

YES: Replace the ECM or PCM . On completion, verify that the DTC is not reset.

NO: A poor connection, open circuit or other intermittent malfunction is present in the CAN bus lines between the ECM or PCM and the ETACS-ECU (Refer to How to Cope with Intermittent Malfunction).

STEP 5. Recheck for diagnostic trouble code.

Check again if the DTC is set.
1. Turn the ignition switch to the "ON" position.
2. Check if the DTC is set.
3. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the DTC set?

YES: Replace the ETACS-ECU. When the ETACS-ECU is replaced, register the encrypted code. Refer to Encrypted Code Registration Criteria Table in Antitheft and Alarm Systems. On completion, verify that the DTC is not reset.

NO: A poor connection, open circuit or other intermittent malfunction is present in the CAN bus lines between the ECM or PCM and the ETACS-ECU (Refer to How to Cope with Intermittent Malfunction).