Multiport Fuel Injection (MFI)

DTC U1110: A/C-ECU TIME-OUT

CAUTION:

- If the ECM [M/T] or the PCM [A/T] output the DTC U1110, make sure to diagnose the CAN bus line.
- Before replacing the ECU, make sure that the communication circuit is operating normally.

DTC SET CONDITIONS

Check Conditions

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

- Unable to receive A/C-ECU signals through the CAN bus line.

COMMENT

Current Trouble

- Some of the possible causes are a harness or connector damage between the ECM [M/T] or the PCM [A/T] and the A/C-ECU on the CAN bus line, a failure in the A/C-ECU power supply system, a failure in the A/C-ECU, or a failure in the ECM [M/T] or the PCM [A/T].
Past Trouble

- Proceed to troubleshoot based on a harness or connector damage on the CAN bus line between the ECM [M/T] or the PCM [A/T] and A/C-ECU, and a failure in the A/C power supply system. Refer to "How to cope with past trouble" How to Cope With Intermittent Malfunctions ).

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, ECM [M/T] or PCM [A/T] stores DTC U1110 (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. In this case, refer to How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions How to Cope With Intermittent Malfunctions. 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 CAN Bus Line Diagnostics Flow).

TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)

- CAN line harness damage or connector damage.
- A/C-ECU failed.
- ECM failed. [M/T]
- PCM failed. [A/T]

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. CAN Bus Diagnostics Chart.
Then go to Step 6.

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

(1)Connect scan tool MB991958 to the data link connector.
(2)Turn the ignition switch to the "ON" position.
(3)Read the A/C-DTC.
(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the A/C-DTC set?

YES Automatic Air Conditioning.

NO Go to Step 3.

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

(1)Connect scan tool MB991958 to the data link connector.
(2)Turn the ignition switch to the "ON" position.
(3)Read the combination ETACS-DTC.
(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is DTC U1110 set?

YES Go to Step 4.

NO Go to Step 5.

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

(1)Connect scan tool MB991958 to the data link connector.
(2)Turn the ignition switch to the "ON" position.
(3)After the MFI-DTC has been deleted, read the MFI-DTC again.
(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is DTC U1110 set?

YES Replace the A/C-ECU. Then go to Step 6.

NO It can be assumed that this malfunction is intermittent of CAN bus line between ECM [M/T] or PCM [A/T] and A/C-ECU. How to Cope With Intermittent Malfunctions.

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

(1)Connect scan tool MB991958 to the data link connector.
(2)Turn the ignition switch to the "ON" position.
(3)After the MFI-DTC has been deleted, read the MFI-DTC again.
(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is DTC U1110 set?

YES Replace the ECM or the PCM. When the ECM or the PCM is replaced, register the encrypted code. Immobilizer System.
Then go to Step 6.

NO It can be assumed that this malfunction is intermittent of CAN bus line between ECM [M/T] or PCM [A/T] and A/C-ECU. How to Cope With Intermittent Malfunctions.

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