Whenever the ECU
is replaced, ensure that the communication circuit is normal.
TROUBLE JUDGMENT
With the ignition switch at the ON position and the system voltage at 10 -16
V (data from ETACS-ECU), if the combination meter detects the abnormal resistance of fuel gauge
unit circuit for 64 seconds continuously, the diagnosis code No. B1201 is stored.
PROBABLE CAUSES
Damaged harness wires and connectors
Malfunction of fuel pump and gauge unit (main)
Malfunction of fuel gauge unit (sub)
Malfunction of combination meter
DIAGNOSIS PROCEDURE
STEP 1. Connector check: D-22 fuel pump and gauge unit (main)
connector
Q.
Is the check result normal?
Go to Step 2.
Repair the connector, and then go to Step 11.
STEP 2. Check of fuel gauge (main) circuit
(1)Disconnect the D-22 fuel pump and fuel gauge unit (main) connector.
(2)Use the special tool Check harness (MB991219) to connect a test lamp (12 V - 3.4
W) between the wiring harness connector terminals 1 and 2.
(3)Turn the ignition switch to the ON position.
(4)Check if the test lamp illuminates. OK: Illuminates
Q.
Is the check result normal?
Go to Step 8.
Go to Step 3.
STEP 3. Resistance measurement at the D-22 fuel pump and gauge unit
(main) connector
(1)Disconnect the fuel pump and gauge unit (main) connector, the measure at the harness
side.
(2)Turn the ignition switch to the OFF (LOCK) position.
(3)Disconnect the negative battery terminal.
(4)Measure the resistance between the D-22 fuel pump and gauge unit (main) connector
terminal No. 1 and the body earth. OK: Continuity exists (2 Ω
or less)
Q.
Is the check result normal?
Go to Step 5.
Go to Step 4.
STEP 4. Check the wiring harness between the D-22 fuel pump and gauge
unit (main) connector terminal No. 1 and the body earth.
Q.
Is the check result normal?
Go to Step 11.
Repair the wiring harness, and then go to Step 11.
STEP 5. Connector check: C-03 combination meter connector and D-24
fuel gauge unit (sub) connector
Q.
Is the check result normal?
Go to Step 6.
Repair the connector, and then go to Step 10.
STEP 6. Check the wiring harness between the C-03 combination meter
connector terminal No. 18 and the D-24 fuel gauge unit (sub) connector terminal No. 2
note
Before the wiring harness check, check the intermediate connectors C-35 and D-05, and
repair them if necessary.
Q.
Is the check result normal?
Go to Step 7.
Repair the wiring harness, and then go to Step 10.
STEP 7. Check the wiring harness between the D-24 fuel gauge unit
(sub) connector terminal No. 1 and the D-22 fuel pump and gauge unit (main) connector terminal
No. 2.
note
Before the wiring harness check, check the intermediate connector D-05, and repair them
if necessary.
Q.
Is the check result normal?
Go to Step 9.
Repair the wiring harness, and then go to Step 10.
STEP 8. M.U.T.-III actuator test
Item 03: Fuel gauge (target value): 0 →100%
OK: The fuel gauge operates.
Q.
Is the check result normal?
Go to Step 9.
Replace the combination meter, and then go to Step 11.
STEP 9. Check whether the diagnosis code is reset.
Check again if the diagnosis code is set to the combination meter.
(1)Erase the diagnosis code.
(2)Turn the ignition switch from "LOCK" (OFF) position to "ON" position.
(3)Check if diagnosis code is set.
Q.
Is the diagnosis code set?
Replace the fuel pump and gauge unit, and then go to Step 11.
The diagnosis is complete.
STEP 10. Check whether the diagnosis code is reset.
Check again if the diagnosis code is set to the combination meter.
(1)Erase the diagnosis code.
(2)Turn the ignition switch from "LOCK" (OFF) position to "ON" position.
(3)Check if diagnosis code is set.
Q.
Is the diagnosis code set?
Replace the fuel gauge unit (sub), and then go to Step 11.
The diagnosis is complete.
STEP 11. Check whether the diagnosis code is reset.
Check again if the diagnosis code is set to the combination meter.
(1)Erase the diagnosis code.
(2)Turn the ignition switch from "LOCK" (OFF) position to "ON" position.
)
)
)
)
)
)
Go to Step 2.
Repair the connector, and then go to Step 11.