1998 OPEL FRONTERA check engine

6E–67 4JX1–TC ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0118 (Flash DTC 14)
ECT Sensor High Voltage
060RW129
Circuit Description
The engine coolant temperature (ECT) sensor is a
thermistor mounted in on a coolant crossover pipe at the
rear of the engine. The Engine Control Module ECM
applies a voltage (about 5 volts) through a pull-up resistor
to the ECT signal circuit. When the engine coolant is cold,
the sensor (thermistor) resistance is high, therefore the
ECM will measure a high signal voltage. As the engine
coolant warms, the sensor resistance becomes less, and
the ECT signal voltage measured at the ECM drops.
Action Taken When the DTC Sets
The ECM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.
Conditions for Clearing the MIL/DTC
DTC P0118 can be cleared by using the Tech 2 “Clear
Info” function or by disconnecting the ECM battery
feed.
Diagnostic Aids
Check for the following conditions:
Poor connection at ECM – Inspect harness connectors
for backed-out terminals, improper mating, broken
locks, improperly formed or damaged terminals, and
poor terminal-to-wire connection.
Damaged harness – Inspect the wiring harness for
damage. If the harness appears to be OK, observe the
ECT display on the Tech 2 while moving connectors
and wiring harnesses related to the ECT sensor. A
change in the ECT display will indicate the location of
the fault.
If DTC P0118 cannot be duplicated, the information
included in the Failure Records data can be useful in
determining vehicle mileage since the DTC was last set.

6E–68
4JX1–TC ENGINE DRIVEABILITY AND EMISSIONS
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Chart.
2. Verifies that the fault is present.
3. If DTC P0118 can be repeated only by duplicating
the Failure Records conditions, refer to the
“Temperature vs. Resistance Value” table. The
table may be used to test the ECT sensor at various
temperatures to evaluate the possibility of a
“shifted” sensor that may be shorted above or below
a certain temperature. If this is the case, replace
the ECT sensor. If the ECT sensor appears to be
OK, the fault is intermittent; refer to
Diagnostic Aids.
Engine Coolant Temperature Sensor
CFOhms
Temperature vs. Resistance Values
(approximate)
80176332
25772796
15594450
DTC P0118 – ECT Sensor High Voltage
StepActionVa l u e ( s )Ye sNo
1Was the “On-Board Diagnostic (OBD) System Check”
performed?
—Go to Step 2
Go to OBD
System
Check
21. Ignition “ON,” engine “OFF.”
2. Observe the “Eng Cool Temp” display on the Tech 2.
Is the “Eng Cool Temp” below the specified value?
–39C
(–38
F)Go to Step 4Go to Step 3
31. Ignition “ON,” engine “OFF.”
2. Review and record Tech 2 Failure Records data.
3. Operate the vehicle within Failure Records
conditions as noted.
4. Using a Tech 2, monitor the “ DTC” info for DTC
P0118.
Does the Tech 2 indicate DTC P0118 failed?
—
Refer to Te s t
Description
Refer to
Diagnostic
Aids
41. Disconnect the ECT sensor electrical connector.
2. Jumper the ECT signal circuit and the sensor
ground circuit together at the ECT sensor harness
connector.
3. Observe the “Eng Cool Temp” display on the Tech 2.
Is the “Eng Cool Temp” at the specified value?
140C
(284
F)Go to Step 6Go to Step 5
51. Jumper the ECT signal circuit at the ECT sensor
harness connector to chassis ground.
2. Observe the “Eng Cool Temp” display on the Tech 2.
Is the “Eng Cool Temp” at the specified value?
140C
(284
F)Go to Step 7Go to Step 8
6Check for poor connections at the ECT sensor and
replace terminals if necessary.
Did any terminals require replacement?
—Verify repairGo to Step 10
71. Ignition “OFF.”
2. Disconnect the ECM, and check the ECT sensor
ground circuit for an open.
3. If the ECT sensor ground circuit is open, repair it as
necessary.
Was the ECT sensor ground circuit open?
—Verify repairGo to Step 9

6E–69 4JX1–TC ENGINE DRIVEABILITY AND EMISSIONS
DTC P0118 – ECT Sensor High Voltage
StepNo Ye s Va l u e ( s ) Action
81. Ignition “OFF.”
2. Disconnect the ECM, and check the ECT signal
circuit for an open.
3. If the ECT sensor signal circuit is open, repair it as
necessary.
Was the ECT signal circuit open?
—Verify repairGo to Step 9
9Check for a poor sensor ground or ECT signal circuit
terminal connection at the ECM and replace
terminal(s) if necessary.
Did any of the terminals need to be replaced?
—Verify repairGo to Step 11
10Replace the ECT sensor.
Is the action complete?
—Verify repair—
11Replace the ECM (Refer to the Data Programming in
Case of ECM change).
Is the action complete?
—Verify repair—

6E–70
4JX1–TC ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0121 (Flash DTC 33)
AP Sensor Rationality
060RW134
Circuit Description
The accel position (AP) sensor circuit provides a voltage
signal that changes relative to throttle blade angle.
The AP signal is one of the most important inputs used by
the Engine Control Module ECM for fuel volume control
and many of the ECM-controlled outputs. If the ECM
detects an out-of-range condition, DTC P0121 will set.
Action Taken When the DTC Sets
The ECM will illuminate the malfunction indicator lamp
(MIL) after fault is detected.
The ECM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.
Conditions for Clearing the MIL/DTC
DTC P0121 can be cleared by using the Tech 2 “Clear
info ” function or by disconnecting the ECM battery
feed.
Diagnostic Aids
Check for the following conditions:
Poor connection at ECM – Inspect harness connectors
for backed-out terminals, improper mating, broken
locks improperly formed or damaged terminals, and
poor terminal-to-wire connection.
Damaged harness – Inspect the wiring harness for
damage. If the harness appears to be OK, observe the
ECT display on the Tech 2 while moving connectors
and wiring harnesses related to the sensor. A change
in the display will indicate the location of the fault.
If DTC P0121 cannot be duplicated, the information
included in the Failure Records data can be useful in
determining vehicle mileage since the DTC was last set.

6E–71 4JX1–TC ENGINE DRIVEABILITY AND EMISSIONS
DTC P0121 –AP Sensor Rationality
StepActionVa l u e ( s )Ye sNo
1Was the “On-Board Diagnostic (OBD) System Check”
performed?
—Go to Step 2
Go to OBD
System
Check
2Check the Idle SW.
Was the Idle SW circuit open or darmage?
—
Replace the
Idle SW
circuit
Go to Step 3
3Observe the AP angle reading on the Tech 2 while
slowly opening the throttle.
Does the AP angle increase steadily and evenly from
the closed throttle value to the wide open throttle
value?Closed
throttle = 0%
Wide open
throttle =
100%
Refer to
Diagnostic
Aids
Go to Step 4
41. Disconnect the AP sensor.
2. Observe the AP sensor reading on the Tech 2.
Is the AP sensor reading near the specified value?
0 VGo to Step 5Go to Step 6
51. Connect a test light between the 5 volt reference
“J2” circuit and the AP sensor signal circuit at the AP
sensor harness connector.
2. Observe the AP sensor reading on the Tech 2.
Is the AP sensor reading at the specified value?
5 VGo to Step 8Go to Step 7
6Check the following items:
1. AP signal circuit for a short to voltage.
2. AP sensor ground circuit for high resistance
between the ECM and the AP sensor.
3. AP sensor ground circuit for a poor connection.
4. If a problem is found, repair wiring harness as
necessary.
Was a problem found?
—Verify repairGo to Step 9
7Check the following items:
1. AP signal circuit or 5 volt reference “J2” circuit for a
poor connection.
2. AP signal circuit or 5 volt reference “J2” circuit for
high resistance between the ECM and the AP
sensor.
3. If a problem is found, repair wiring harness as
necessary.
Was a problem found?
—Verify repairGo to Step 9
8Replace the AP sensor.
Is the action complete?
—Verify repair—
9Replace the ECM (Refer to the Data Programming in
Case of ECM change).
Is the action complete?
—Verify repair—

6E–72
4JX1–TC ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0122 (Flash DTC 21)
AP Sensor Low Voltage
060RW134
Circuit Description
The accelerator position (AP) sensor circuit provides a
voltage signal that changes relative to throttle blade
angle.
The AP signal is used by the Engine Control Module ECM
for fuel volume control and many of the ECM-controlled
outputs.
Action Taken When the DTC Sets
The ECM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.
Conditions for Clearing the MIL/DTC
DTC P0122 can be cleared by using the Tech 2 “Clear
Info” function or by disconnecting the ECM battery
feed.
Diagnostic Aids
Check for the following conditions:
Poor connection at ECM – Inspect harness connectors
for backed-out terminals, improper mating, broken
locks, improperly formed or damaged terminals, and
poor terminal-to-wire connection.
Damaged harness – Inspect the wiring harness for
damage. If the harness appears to be OK, observe the
throttle position display on the Tech 2 while moving
connectors and wiring harnesses related to the TP
sensor. A change in the display will indicate the
location of the fault.
If DTC P0122 cannot be duplicated, the information
included in the Failure Records data can be useful in
determining vehicle mileage since the DTC was last set.
DTC P0122 –AP Sensor Low Voltage
StepActionVa l u e ( s )Ye sNo
1Was the “On-Board Diagnostic (OBD) System Check”
performed?
—Go to Step 2
Go to OBD
System
Check
2Check the AP sensor signal circuit.
Was the AP sensor signal circuit open or darmage?
—
Replace the
APS circuit
Go to Step 3

6E–73 4JX1–TC ENGINE DRIVEABILITY AND EMISSIONS
DTC P0122 –AP Sensor Low Voltage
StepNo Ye s Va l u e ( s ) Action
31. Ignition “ON,” engine “OFF.”
2. With the throttle closed, observe the “AP Sensor”
display on the Tech 2.
Is the “AP Sensor” below the specified value?
0.1 VGo to Step 5Go to Step 4
41. Ignition “ON,” engine “OFF.”
2. Review and record Tech 2 Failure Records data.
3. Operate the vehicle within Failure Records
conditions as noted.
4. Using a Tech 2, monitor the “DTC” info for DTC
P0122.
Does the Tech 2 indicate DTC P0122 failed?
—Go to Step 5
Refer to
Diagnostic
Aids
51. Ignition “OFF.”
2. Disconnect the AP sensor electrical connector.
3. Jumper the 5 volt reference “J2” circuit and the AP
signal together at the AP sensor harness connector.
4. Ignition “ON.”
Observe the “AP Sensor” display on the Tech 2.
Is the “AP Sensor” at the specified value?
5 VGo to Step 11Go to Step 6
61. Disconnect jumper.
2. Connect a test light between B+ and the AP sensor
signal circuit at the AP sensor harness connector.
Observe the “AP Sensor” display on the Tech 2.
Is the “AP Sensor” at the specified value?
5 VGo to Step 7Go to Step 9
71. Ignition “OFF.”
2. Disconnect the ECM and check the 5 volt reference
“A” circuit for an open or short to ground.
3. If the 5 volt reference “J2” circuit is open or shorted
to ground, repair it as necessary.
Was the 5 volt reference “J2” circuit open or shorted to
ground?
—Verify repairGo to Step 8
8Check the 5 volt reference “J2” circuit for a poor
connection at the ECM and replace the terminal if
necessary.
Did the terminal require replacement?
—Verify repairGo to Step 13
91. Ignition “OFF.”
2. Disconnect the ECM, and check the AP signal
circuit for an open, short to ground, or short to the
sensor ground circuit.
3. If the AP sensor signal circuit is open or shorted to
ground, repair it as necessary.
Was the AP signal circuit open or shorted to ground?
—Verify repairGo to Step 10
10Check the AP sensor signal circuit for a poor
connection at the ECM and replace the terminal if
necessary.
Did the terminal require replacement?
—Verify repairGo to Step 13
11Check the AP sensor signal circuit for a poor
connection at the AP sensor and replace the terminal if
necessary.
Did the terminal require replacement?
—Verify repairGo to Step 12

6E–75 4JX1–TC ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0123 (Flash DTC 21)
AP Sensor High Voltage
060RW134
Circuit Description
The accelerator position (AP) sensor circuit provides a
voltage signal that changes relative to throttle blade
angle.
The TP signal is one of the most important inputs used by
the Engine Control Module ECM for fuel volume control
and many of the ECM-controlled outputs.
Action Taken When the DTC Sets
The ECM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.
Conditions for Clearing the MIL/DTC
DTC P0123 can be cleared by using the Tech 2 “Clear
Info” function or by disconnecting the ECM battery
feed.
Diagnostic Aids
Check for the following conditions:
Poor connection at ECM – Inspect harness connectors
for backed-out terminals, improper mating, brokenlocks, improperly formed or damaged terminals, and
poor terminal-to-wire connection.
Damaged harness – Inspect the wiring harness for
damage. If the harness appears to be OK, observe the
AP sensor display on the Tech 2 while moving
connectors and wiring harnesses related to the TP
sensor. A change in the display will indicate the
location of the fault.
Faulty AP sensor – With the ignition key “ON,” engine
“OFF,” observe the AP sensor display on the Tech 2
while slowly depressing the accelerator to wide open
throttle. If a voltage over 4.88 volts is seen at any point
in normal accelerator travel, replace the AP sensor.
If DTC P0123 cannot be duplicated, the information
included in the Failure Records data can be useful in
determining vehicle mileage since the DTC was last set.
Test Description
Number (s) below refer to the step number(s) on the
Diagnostic Chart.
8. Components that share the AP sensor 5 volt reference
“A” circuit include the following device: