Headup Display Malfunction: Procedure

1. Check the symptom of the headup display (combination meter mirror ECU).

   Result

   Result	Proceed to
   Headup display (combination meter mirror ECU) does not operate at all.	A
   Cruise information display does not change.	B

B → See step   3 

A: Go to next step 

1. Disconnect the L139 connector.
   Fig 1: Identifying L139 Headup Display Connector Terminal

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   L139-13 (12V) - Body ground	Power switch on (IG)	11 to 14 V

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

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   L139-16 (GND) - Body ground	Always	Below 1 Ω

   TEXT IN ILLUSTRATION
   
   

   *1	Front view of wire harness connector (to Headup Display (Combination Meter Mirror ECU))

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK → See step   8 

1. Connect the Techstream to the DLC3.
2. Turn the power switch on (IG).
3. Turn the Techstream ON.
4. Enter the following menus: Body Electrical / Combination Meter / Data List.
5. Check the values by referring to the table below.
   COMBINATION METER
   
   

   Tester Display	Measurement Item/Range	Normal Condition	Diagnostic Note
   Head Up Display Switch (Up)	Headup display position up switch condition	OFF: Headup display position up switch not pressed	-
   		ON: Headup display position up switch pressed	-
   Head Up Display Switch (Down)	Headup display position down switch condition	OFF: Headup display position down switch not pressed	-
   		ON: Headup display position down switch pressed	-
   Head Up Display Switch (Main)	Headup display main switch condition	OFF: Headup display main switch not pressed	-
   		ON: Headup display main switch pressed	-

   OK

   Each switch condition displayed on the Techstream changes with the actual switch operation.

B → See step   4 

A → See step   9 

1. Disconnect the L139 and L57 connectors.
2. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   L139-17 (BKR) - L136-5 (BKR)	Always	Below 1 Ω
   L139-17 (BKR) - Body ground	Always	10 kΩ or higher
   L139-18 (LAT) - L136-6 (LAT)	Always	Below 1 Ω
   L139-18 (LAT) - Body ground	Always	10 kΩ or higher
   L139-19 (CLKH) - L136-6 (CLKH)	Always	Below 1 Ω
   L139-19 (CLKH) - Body ground	Always	10 kΩ or higher
   L139-20 (CLKL) - L136-8 (CLKL)	Always	Below 1 Ω
   L139-20 (CLKL) - Body ground	Always	10 kΩ or higher
   L139-21 (SIH) - L136-9 (SIH)	Always	Below 1 Ω
   L139-21 (SIH) - Body ground	Always	10 kΩ or higher
   L139-22 (SIL) - L136-10 (SIL)	Always	Below 1 Ω
   L139-22 (SIL) - Body ground	Always	10 kΩ or higher
   L139-23 (WE) - L136-11 (WE)	Always	Below 1 Ω
   L139-23 (WE) - Body ground	Always	10 kΩ or higher
   L139-2 (STP1) - L136-14 (STP1)	Always	Below 1 Ω
   L139-2 (STP1) - Body ground	Always	10 kΩ or higher
   L139-3 (STP2) - L136-15 (STP2)	Always	Below 1 Ω
   L139-3 (STP2) - Body ground	Always	10 kΩ or higher
   L139-4 (STP3) - L136-16 (STP3)	Always	Below 1 Ω
   L139-4 (STP3) - Body ground	Always	10 kΩ or higher
   L139-5 (STP4) - L136-17 (STP4)	Always	Below 1 Ω
   L139-5 (STP4) - Body ground	Always	10 kΩ or higher

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Disconnect the L57 connector.
   Fig 2: Identifying L57 Trip Switch Connector Terminal

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Switch Condition	Specified Condition
   2 (CH) - 12 (E)	HUD/MODE switch pressed	Below 1 Ω
   2 (CH) - 12 (E)	Always	10 kΩ or higher
   12 (E) - 14 (HDD)	Down switch pressed	Below 1 Ω
   12 (E) - 14 (HDD)	Always	10 kΩ or higher
   12 (E) - 15 (HDU)	Up switch pressed	Below 1 Ω
   12 (E) - 15 (HDU)	Always	10 kΩ or higher

   TEXT IN ILLUSTRATION
   
   

   *1	Trip Switch
   *2	Component without harness connected (Trip Switch)

NG → See step   10 

OK: Go to next step 

1. Disconnect the L27, L57, and L137 connectors.
2. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   L57-1 (CS) - L27-2 (TC O)	Always	Below 1 Ω
   L57-1 (CS) - Body ground	Always	10 kΩ or higher
   L57-9 (HOUR) - L27-12 (HOUR)	Always	Below 1 Ω
   L57-9 (HOUR) - Body ground	Always	10 kΩ or higher
   L57-10 (MIN) - L27-13 (MIN)	Always	Below 1 Ω
   L57-10 (MIN) - Body ground	Always	10 kΩ or higher
   L57-11 (RST) - L27-17 (RST)	Always	Below 1 Ω
   L57-11 (RST) - Body ground	Always	10 kΩ or higher
   L57-12 (E) - L137-2 (E)	Always	Below 1 Ω
   L57-12 (E) - Body ground	Always	10 kΩ or higher
   L57-15 (HDU) - L137-7 (HUDU)	Always	Below 1 Ω
   L57-15 (HDU) - Body ground	Always	10 kΩ or higher
   L57-14 (HDD) - L137-4 (HUDD)	Always	Below 1 Ω
   L57-14 (HDD) - Body ground	Always	10 kΩ or higher
   L57-3 (TAIL) - L137-3 (HUDI)	Always	Below 1 Ω
   L57-3 (TAIL) - Body ground	Always	10 kΩ or higher
   L57-2 (CH) - L137-8 (HUDO)	Always	Below 1 Ω
   L57-2 (CH) - Body ground	Always	10 kΩ or higher
   L57-6 (NVI) - L137-9 (IIND)	Always	Below 1 Ω
   L57-6 (NVI) - Body ground	Always	10 kΩ or higher
   L57-7 (NVM) - L137-1 (NVSW)	Always	Below 1 Ω
   L57-7 (NVM) - Body ground	Always	10 kΩ or higher

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Replace the headup display (combination meter mirror ECU) with a new or a known good one. Refer to DISASSEMBLY - Step 8 .

   OK

   The operation of the headup display (combination meter mirror ECU) returns to normal.

NG → See step   9 

OK → END