Manual Air Conditioning

DTC U1100: ECM [M/T] or PCM [A/T] Time-out (Related to Engine)

CAUTION:
If DTC U1100 is set in the A/C-ECU, diagnose the CAN main bus line.

CAUTION:
Whenever the ECU is replaced, ensure that the communication circuit is normal.

TROUBLE JUDGMENT

The A/C-ECU receives engine control system-related signals from the ECM [M/T] or PCM [A/T] via CAN bus lines. If the A/C-ECU cannot receive the necessary signals, DTC U1100 will be set.

PROBABLE CAUSES

- Malfunction of the harness (CAN line is open/shorted to ground)
- Malfunction of the ECM[ M/T] or PCM[ A/T]
- Malfunction of the A/C-ECU
- Malfunction of connector

DIAGNOSIS

Required Special Tools:

- 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 to the data link connector.
(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 lines Precautions on How to Repair the CAN Bus Line(s)).

STEP 2. Using scan tool MB991958 read the ECM [M/T] or PCM [A/T] diagnostic trouble code.

Check whether an engine or automatic transaxle DTC are set or not.

(1)Turn the ignition switch to the "ON" position.

(2)Check for engine and automatic transaxle DTCs.

(3)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the check result satisfactory?

YES Go to Step 3.
NO Diagnose the ECM [M/T] or PCM [A/T] Multiport Fuel Injection (MFI) [2.4L ENGINE] or Diagnostic Trouble Code Multiport Fuel Injection (MFI) [3.8L ENGINE]).
STEP 3. Using scan tool MB991958, check 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
- ABS-ECU
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 check result satisfactory?

YES Go to Step 5.
NO Go to Step 4.
STEP 4. Using scan tool MB991958 read the ECM [M/T] or PCM [A/T] diagnostic trouble code.

Check whether an engine and automatic transaxle DTCs are set or not.

(1)Turn the ignition switch to the "ON" position.

(2)Check for engine and automatic transaxle DTCs.

(3)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the check result satisfactory?

YES The procedure is complete.
NO Replace the heater control.
STEP 5. Replace the A/C-ECU and then recheck the DTC.

Check again if the DTC is set.

(1)Connect scan tool MB991958 to the data link connector

(2)Turn the ignition switch to the "ON" position.

(3)Check if the DTC is set.

(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the check result satisfactory?

YES The procedure is complete.
NO Go to Step 1.