Rear Window Defogger System does not Operate: Procedure

1. Check that the engine starts normally.

   OK

   Engine starts normally.

NG → See step   10 

OK: Go to next step 

1. Using the Techstream ACTIVE TEST, generate a control command and then check that the rear window defogger operates.
   AIR CONDITIONING AMPLIFIER (A/C ECU)
   
   

   Tester Display	Test Part	Control Range
   Defogger Relay (Rear)	Operate rear window defogger	OFF / ON

   RESULT
   
   

   Result	Proceed to
   Rear window defogger operates normally	A
   Rear window defogger operates abnormally	B

B → See step   4 

A: Go to next step 

1. Temporarily replace the multi-display with a new or normally functioning one.
2. Check that the malfunction disappears.

   OK

   Malfunction disappears.

NG → REPLACE AIR CONDITIONING AMPLIFIER 

OK → REPLACE MULTI-DISPLAY 

1. Remove the DEFOG fuse from the engine room No. 1 relay block.
2. Remove the AM2 fuse from the main body ECU RH.
3. Remove the LH-IG fuse from the main body ECU LH.
4. Measure the resistance of the fuses.

   Standard resistance

   Below 1 Ω

NG → REPLACE FUSE 

OK: Go to next step 

Fig 1: Identifying Defogger Relay

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

1. Remove the defogger relay from the engine room No. 1 relay block.
2. Measure the resistance of the relay.

   Standard resistance

   Tester Connection	Specified Condition
   3 - 4	Below 1 Ω
   3 - 5	10 kΩ or higher
   3 - 4	10 kΩ or higher (when battery voltage is applied to terminals 1 and 2)
   3 - 5	Below 1 Ω (when battery voltage is applied to terminals 1 and 2)

NG → REPLACE DEFOGGER RELAY 

OK: Go to next step 

Fig 2: Identifying Defogger Relay From Engine Room No. 1 Relay Blocy & A53 ECM Connector Terminals

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

1. Remove the defogger relay from the engine room No. 1 relay block.
2. Disconnect the A53 ECM connector.
3. Measure the voltage of the wire harness side connectors.

   Standard voltage

   Tester Connection	Condition	Specified Condition
   Relay block defogger relay terminal 1 - Body ground	Power switch ON (IG)	10 to 14 V
   Relay block defogger relay terminal 5 - Body ground	Always	10 to 14 V

4. Measure the resistance of the wire harness side connectors.

   Standard resistance

   Tester Connection	Specified Condition
   Relay block defogger relay terminal 2 - A53-14 (RDEF)	Below 1 Ω

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

Fig 3: Identifying V20 & U20 Rear Window Defogger & Defogger Relay From The Engine Room No. 1 Relay Block

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

1. Disconnect the U20 and V20 defogger connectors.
2. Disconnect the defogger relay from the engine room No. 1 relay block.
3. Measure the resistance of the wire harness side connectors.

   Standard resistance

   Tester Connection	Specified Condition
   V20-1 - Relay block DEFOG relay terminal 3	Below 1 Ω
   U20-1 - Body ground	Below 1 Ω
   Relay block DEFOG relay terminal 4 - Body ground	Below 1 Ω
   V20-1 - Body ground	10 kΩ or higher

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Turn the power switch ON (IG).
2. Turn the defogger switch ON.
3. Check the voltage at the center of each defogger wire, as shown in the illustration.
   Fig 4: Identifying Voltage At Center Of Defogger Wire Using A Voltmeter

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   Standard voltage

   Voltage	Criteria
   Approx. 5 V	Wire is not broken
   Approx. 10 or 0 V	Wire is broken

   HINT: 

   If there is approximately 10 V, the wire may be faulty between the center of the wire and the wire end on the battery side. If there is no voltage, the wire may be faulty between the center of the wire and the wire end on the ground side.

   NOTE:

   When measuring voltage, wrap a piece of tin foil around the tip of the negative tester probe and press the foil against the wire with your finger, as shown in the illustration.

4. Place the voltmeter's positive (+) lead against the defogger wire on the battery side.
   Fig 5: Placing Voltmeter's Positive (+) Lead Against Defogger Wire On Battery Side

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
5. Place the voltmeter's negative (-) lead with the foil strip against the wire on the ground side.
6. Slide the positive (+) lead from the battery side to the ground side.
7. The point where the voltage drops from approximately 10 V to 0 V is where the defogger wire is broken.

   HINT: 

   If the defogger wire is not broken, the voltmeter should indicate 0 V at the positive (+) end of the defogger wire and gradually increase to approximately 12 V as the meter probe is moved to the other end.

NG → REPAIR REAR WINDOW DEFOGGER WIRE 

OK: Go to next step 

1. Temporarily replace the ECM with a new or normally functioning one.
2. Check that the malfunction disappears.

   OK

   Malfunction disappears.

NG → REPLACE AIR CONDITIONING AMPLIFIER (A/C ECU) 

OK → REPLACE ECM