2004 ISUZU TF SERIES check engine

BRAKE CONTROL SYSTEM 5A-79

DTC C0271 (Flash Code 71) ECU Failure or Valve +B Circuit Open



RTW45AMF000201

Step Action
Value(s) Yes No
1 Was the “Basic Diagnostic Flow Chart” performed?
- Go to Step 2 Go to Basic
Diagnostic
Flow Chart
2 1. Ignition “OFF”.
2. Check the EHCU circuit for an open, short to
ground, or short to voltage. Also, check the EHCU
ignition feed circuit for an open or short to ground
and the EHCU ground circuit for an open or short to
voltage.
3. If a problem is found, repair as necessary.
Was a problem found?
- Verify repair Go to Step 3
3 1. Ignition “ON,” engine “OFF.”
2. Select “Display DTCs” with the Tech 2.
Note: Perform the various tests (actuator test, test
run, brake test, etc.) then observe the DTC with a
Tech2.
Are any DTCs stored? - Go to Step 4 Verify repair
4 Replace EHCU.
Note : Check the EHCU type for specification, when
the EHCU is replaced.
(Specification ; 2WD model or 4WD model)
Was the action complete? - Verify repair -

BRAKE CONTROL SYSTEM 5A-81

Step Action
Value(s) Yes No
6 1. Ignition “OFF”.
2. Check the EHCU circuit for an open, short to
ground, or short to voltage. Also, check the EHCU
ignition feed circuit for an open or short to ground
and the EHCU ground circuit for an open or short to
voltage.
3. If a problem is found, repair as necessary.
Was a problem found?
- Verify repair Go to Step 7
7 1. Ignition “ON,” engine “OFF.”
2. Select “Display DTCs” with the Tech 2.
Note: Perform the various tests (actuator test, test
run, brake test, etc.) then observe the DTC with a
Tech2.
Are any DTCs stored? - Go to Step 8 Verify repair
8 Replace EHCU.
Note : Check the EHCU type for specification, when
the EHCU is replaced.
(Specification ; 2WD model or 4WD model)
Was the action complete? - Verify repair -

5A-82 BRAKE CONTROL SYSTEM

DTC C0276 (Flash Code 76) G-Sensor Malfunction


RTW35AMF000301

Step Action
Value(s) Yes No
1 Was the “Basic Diagnostic Flow Chart” performed?
- Go to Step 2 Go to Basic
Diagnostic
Flow Chart
2 1. Check for a poor connection at the G-sensor
harness connector.
2. If a problem is found, repair as necessary.
Was a problem found?
- Verify repair Go to Step 3
3 1. Ignition “OFF”, disconnect the G-sensor and
EHCU.
2. Ignition “ON”, engine “OFF”.
3. Check the supply voltage to G-sensor.
Was the value normal? Battery
Voltage Go to Step 5 Go to Step 4
4 Repair or replace the power supply circuit.
Was the action complete? - Verify repair -
5 1. Check the circuit between EHCU and G-sensor.
(Circuit for an open, short to ground, or short to
voltage.)
2. If a problem is found, repair as necessary.
Was a problem found?
- Verify repair Go to Step 6

BRAKE CONTROL SYSTEM 5A-83

Step Action
Value(s) Yes No
6 1. Remove the G-sensor.
2. Reconnect G-sensor and EHCU
3. Install the Tech 2.
4. Ignition "ON", engine "OFF".
5. Observe the G-sensor reading on Tech 2.
If G-sensor inclines, reading voltage will change.
Is the reading voltage between specified value? 1.0 - 4.0V Go to Step 7 Go to Step 8
7 1. Ignition "OFF".
2. Install the G-sensor.
3. Install the Tech 2.
4. Ignition "ON", engine "OFF".
5. Select "Display DTCs" with the Tech 2.
Are any DTCs stored? - Go to Step 8 Verify repair
8 1. Replace G-sensor.
2. Select "Display DTCs" with the Tech 2.
Note: Perform the various tests (actuator test, test
run, brake test, etc.) then observe the DTC with a
Tech2.
Are any DTCs stored? - Go to Step 9 Verify repair
9 Replace EHCU.
Note : Check the EHCU type for specification, when
the EHCU is replaced.
(Specification ; 2WD model or 4WD model)
Was the action complete? - Verify repair -

5A-84 BRAKE CONTROL SYSTEM

DTC C0277 (Flash Code 77) Power Supply Low Input
DTC C0278 (Flash Code 78) Power Supply High Input



RTW45AMF000201

Step Action
Value(s) Yes No
1 Was the “Basic Diagnostic Flow Chart” performed?
- Go to Step 2 Go to Basic
Diagnostic
Flow Chart
2 1. Check for a poor connection at EHCU
2. If a problem is found, repair as necessary.
Was a problem found?
- Verify repair Go to Step 3
3 1. Ignition “OFF”, disconnect EHCU.
2. Ignition “ON”, engine “OFF”.
3. Check the supply voltage to EHCU.
Was the value normal? Battery
Voltage Go to Step 5 Go to Step 4
4 Repair or replace the power supply circuit.
Was the action complete? - Verify repair -
5 1. Check the power supply circuit.
(Circuit for an open, short to ground, or short to
voltage.)
2. If a problem is found, repair as necessary.
Was a problem found?
- Verify repair Go to Step 6

BRAKE CONTROL SYSTEM 5A-85

Step Action
Value(s) Yes No
6 1. Ignition “ON,” engine “OFF.”
2. Select “Display DTCs” with the Tech 2.
Note: Perform the various tests (actuator test, test
run, brake test, etc.) then observe the DTC with a
Tech2.
Are any DTCs stored? - Go to Step 7 Verify repair
7 Replace EHCU.
Note : Check the EHCU type for specification, when
the EHCU is replaced.
(Specification ; 2WD model or 4WD model)
Was the action complete? - Verify repair -

BRAKE CONTROL SYSTEM 5A-87

Step Action
Value(s) Yes No
5 1. Ignition "OFF".
2. Connect 2-4WD control unit.
3. Disconnect EHCU.
4. Ignition "ON," engine "OFF."
5. Install the high impedance digital multimeter.
6. Check the transfer (2-4WD control unit) signal
value.
Was the value normal? Transfer 2WD
Mode: 8.3Hz
(
15%)
Transfer 4WD
Mode: 4.2Hz
(
15%) Go to Step 7 Go to Step 6
6 Replace 2-4WD control unit.
Was the action complete?
- Go to Step 7 -
7 1. Ignition “ON,” engine “OFF.”
2. Select “Display DTCs” with the Tech 2.
Note: Perform the various tests (actuator test, test
run, brake test, etc.) then observe the DTC with a
Tech2.
Are any DTCs stored? - Go to Step 8 Verify repair
8 Replace EHCU.
Note : Check the EHCU type for specification, when
the EHCU is replaced.
(Specification ; 2WD model or 4WD model)
Was the action complete? - Verify repair -

BRAKE CONTROL SYSTEM 5A-89

Step Action Value(s) Yes No
4 1. Ignition "OFF".
2. Check for a poor condition at the EHCU harness
connector.
3. Check the EHCU circuit for an open, short to
ground, or short to voltage. Also, check the EHCU
ignition feed circuit for an open or short to ground
and the EHCU ground circuit for an open or short
to voltage.
4. If a problem is found, repair as necessary.
Was a problem found? - Verify repair Go to Step 9
5 1. Ignition "OFF," disconnect the EHCU and G-
sensor.
2. Check the circuit between EHCU and G-sensor.
(short to ground, or short to voltage.)
3. If a problem is found, repair as necessary.
Was a problem found? - Verify repair
Go to Step 6 Go to Step 6
6 1. Remove the G-sensor.
2. Reconnect G-sensor and EHCU
3. Install the Tech 2.
4. Ignition "ON", engine "OFF".
5. Observe the G-sensor reading on Tech 2.
If G-sensor inclines, reading voltage will change.
Is the reading voltage between specified value? 1.0 – 4.0 V Go to Step 7 Go to Step 8
7 1. Ignition "OFF".
2. Install the G-sensor.
3. Install the Tech 2.
4. Ignition "ON", engine "OFF".
5. Select "Display DTCs" with the Tech 2.
Are any DTCs stored? - Go to Step 8 Verify repair
8 1. Replace G-sensor.
2. Select "Display DTCs" with the Tech 2.
Note: Perform the various tests (actuator test, test
run, brake test, etc.) then observe the DTC with a
Tech2.
Are any DTCs stored? - Go to Step 9 Verify repair
9 Replace EHCU.
Note : Check the EHCU type for specification, when
the EHCU is replaced.
(Specification ; 2WD model or 4WD model)
Was the action complete? - Verify repair -