DTC B2556: Operation switch: Diagnosis

Required Special Tools:

MB991223: Harness Set
MB992006: Extra Fine Probe

STEP 1. Using scan tool (M.U.T.-IIISE), check data list.

By using the service data of the HUD, check the input signal of each switch.

CAUTION: To prevent damage to scan tool (M.U.T.-IIISE), always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool (M.U.T.-IIISE).

Connect scan tool (M.U.T.-IIISE). Refer to "HOW TO CONNECT THE SCAN TOOL (M.U.T.-IIISE) ."

Turn the ignition switch to the "ON" position.

When the combiner open/close switch is operated.

Item No.	Item name	Normal condition
1	HUD SW	ON

When the combiner open/close switch is not operated.

Item No.	Item name	Normal condition
1	HUD SW	OFF

When the brightness adjustment switch (+) is operated.

Item No.	Item name	Normal condition
2	Brightness SW (UP)	ON

When the brightness adjustment switch (+) is not operated.

Item No.	Item name	Normal condition
2	Brightness SW (UP)	OFF

When the brightness adjustment switch (-) is operated.

Item No.	Item name	Normal condition
3	Brightness SW (DOWN)	ON

When the brightness adjustment switch (-) is not operated.

Item No.	Item name	Normal condition
3	Brightness SW (DOWN)	OFF

When the angle adjustment switch (UP) is operated.

Item No.	Item name	Normal condition
4	Angle SW (UP)	ON

When the angle adjustment switch (UP) is not operated.

Item No.	Item name	Normal condition
4	Angle SW (UP)	OFF

When the angle adjustment switch (DOWN) is operated.

Item No.	Item name	Normal condition
5	Angle SW (DOWN)	ON

When the angle adjustment switch (DOWN) is not operated.

Item No.	Item name	Normal condition
5	Angle SW (DOWN)	OFF

OK: Normal conditions are displayed for all the items.

Q: Is the check result normal?

YES: Go to Step 5.

NO: Go to Step 2.

STEP 2. Check of short to ground circuit.
- Check of short to ground circuit in O/C, BR+, BR-, AN+, AN- line between HUD connector and body ground.
- Check of short to ground circuit between HUD connector (O/C, BR+, BR-, AN+, AN- terminal) and HUD connector (SW- terminal).
  OK: No continuity.
Q: Is the check result normal?

YES: Go to Step 3.

NO: Repair the connector(s) or wiring harness.
STEP 3. Check the HUD switch.
Check the continuity between the following terminals.

Refer to HUD SWITCH .
- terminal No. 2 - 11
- terminal No. 3 - 11
- terminal No. 7 - 11
- terminal No. 8 - 11
- terminal No. 9 - 11
Q: Is the check result normal?

YES: Go to Step 4.

NO: Replace the HUD switch.

STEP 4. Using scan tool (M.U.T.-IIISE), check data list.