Manual A/C Diagnosis
DTC U0195: Satellite radio tuner CAN timeoutCAUTION:
- If DTC U0195 is set in the A/C-ECU or heater control unit [vehicles without A/C], diagnose the CAN main bus line.
- Whenever the ECU is replaced, ensure that the communication circuit is normal.
TROUBLE JUDGMENT
The A/C-ECU or heater control unit [vehicles without A/C] receives air conditioning operation-related signals from the satellite radio via the CAN bus lines. If any of the air conditioning control-related signals from the satellite radio cannot be received, the diagnostic trouble code U0195 is stored.
TECHNICAL DESCRIPTION (COMMENT)
Current trouble
- Connector(s) or wiring harness in the CAN bus lines between the Satellite Radio and the A/C-ECU or heater control unit [vehicles without A/C], the power supply system to the Satellite Radio, the Satellite Radio itself, or the A/C-ECU or heater control unit [vehicles without A/C] may be defective.
Past trouble
- If DTC U0195 is stored as a past trouble, carry out diagnosis with particular emphasis on wiring and connector(s) in the CAN bus line between the A/C-ECU or heater control unit [vehicles without A/C] and the Satellite Radio, and the power supply system to the Satellite Radio. If the connectors and wiring are normal, and obviously the ECU is the cause of the trouble, replace the ECU. If in doubt, do not replace the ECU.
NOTE: For a past trouble, you cannot find it by the scan tool CAN bus diagnostics even if there is a failure in CAN bus lines. In this case, 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 Explanation about the scan too CAN bus diagnostics). Explanation About the Scan Tool (M.U.T.-III) CAN Bus Diagnostics
TROUBLESHOOTING HINTS
- Malfunction of the Satellite Radio
- Malfunction of the A/C-ECU or heater control unit [vehicles without A/C]
- Damaged harness wires and connectors
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 the Scan Tool (M.U.T.-III)
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
STEP 2. Using scan tool MB991958 read the Satellite Radio diagnostic trouble code.
Check whether an satellite radio DTCs are set or not.
1. Turn the ignition switch to the "ON" position.
2. Check for Satellite Radio DTCs.
3. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the DTC set?
YES : Diagnose the Satellite Radio. Diagnostic Trouble Code Descriptions
NO : Go to Step 3.
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.
- ETACS-ECU
DTC indicating a time-out error related to the Satellite Radio 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 Satellite Radio. On completion, check that the DTC is not reset.
NO : There is an intermittent malfunction such as poor engaged connector(s) or open circuit.
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 A/C-ECU or heater control unit [vehicles without A/C]. On completion, check that the DTC is not reset.
NO : There is an intermittent malfunction such as poor engaged connector(s) or open circuit.