Lost Communication with A/C ECU (U0164)

NOTICE:

• Turn the ignition switch off before measuring the resistances between CAN bus main wires and between CAN bus branch wires.
• Turn the ignition switch off before inspecting CAN bus wires for a ground short.
• After the ignition switch is turned off, check that the key reminder warning system and light reminder warning system are not operating.
• Before measuring the resistance, leave the vehicle as is for at least 1 minute and do not operate the ignition switch, any other switches or the doors. If any doors need to be opened in order to check connectors, open the doors and leave them open.

HINT:

• Operating the ignition switch, any other switches or a door triggers related ECU and sensor communication on the CAN. This communication will cause the resistance value to change.
• Even after DTCs are cleared, if a DTC is stored again after driving the vehicle for a while, the malfunction may be occurring due to vibration of the vehicle. In such a case, wiggling the ECUs or wire harness while performing the inspection below may help determine the cause of the malfunction.

1. RECONFIRM DTC OUTPUT

(a) Reconfirm DTCs.

HINT:

If power management bus DTC U1002 is output from the power management control ECU (Techstream display: PM2 Gateway), troubleshoot for U1002 and check for malfunctions in the power management main bus circuit.

B

GO TO CIRCUITS INDICATED BY OUTPUT DTCS

A

1. CHECK FOR OPEN IN CAN BUS WIRES (AIR CONDITIONING AMPLIFIER BRANCH WIRE)

(a) Turn the ignition switch off.

(b) Disconnect the air conditioning amplifier connector. Text in Illustration *1 Front view of wire harness connector (to Air Conditioning Amplifier)

(c) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

NG

REPAIR OR REPLACE CAN BUS BRANCH WIRE OR CONNECTOR (AIR CONDITIONING AMPLIFIER BRANCH WIRE)

OK

1. CHECK HARNESS AND CONNECTOR (POWER SOURCE TERMINAL)

(a) Turn the ignition switch to ON.

(b) Measure the voltage according to the value(s) in the table below. Standard Voltage: Tester Connection Condition Specified Condition D47-1 (IG+) - Body ground Ignition switch ON 11 to 14 V Text in Illustration *1 Front view of wire harness connector (to Air Conditioning Amplifier)

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (POWER SOURCE CIRCUIT)

OK

1. CHECK HARNESS AND CONNECTOR (GROUND TERMINAL)

(a) Measure the resistance according to the value(s) in the table below. Standard Resistance: Tester Connection Condition Specified Condition D47-13 (GND) - Body ground Always Below 1 Ω Text in Illustration *1 Front view of wire harness connector (to Air Conditioning Amplifier)

OK

REPLACE AIR CONDITIONING AMPLIFIER

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (GROUND CIRCUIT)