Opel Frontera UBS. Manual - part 2139

6E–129

ENGINE DRIVEABILITY AND EMISSIONS

DTC P0118 – ECT Sensor Circuit High Voltage

  (Cont'd)

Step

No

Yes

Value(s)

Action

7

1. Ignition “OFF.”
2. Disconnect the PCM, 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 repair

Go to 

Step 9

8

1. Ignition “OFF.”
2. Disconnect the PCM, 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 repair

Go to 

Step 9

9

Check for a poor sensor ground or ECT signal circuit
terminal connection at the PCM and replace
terminal(s) if necessary.

Did any of the terminals need to be replaced?

—

Verify repair

Go to 

Step 11

10

Replace the ECT sensor.

Is the action complete?

—

Verify repair

—

11

Replace the PCM.

IMPORTANT: The replacement PCM must be
programmed.  Refer to 

UBS 98model year Immobilizer

Workshop Manual.

Is the action complete?

—

Verify repair

—

6E–130

ENGINE DRIVEABILITY AND EMISSIONS

Diagnostic Trouble Code (DTC) P0121 TP System Performance

D06RW028

Circuit Description

The throttle position (TP) sensor circuit provides a voltage
signal that changes relative to throttle blade angle.  The
signal voltage will vary from about 0.6 volts at closed
throttle to about 4.5 volts at wide open throttle (WOT).
The TP signal is used by the powertrain control module
(PCM) for fuel control and many of the PCM-controlled
outputs.  The PCM monitors throttle position and
compares actual throttle position from the TP sensor to a
predicted TP value calculated from engine speed.  If the
PCM detects an out-of-range condition, DTC P0121 will
set.

Conditions for Setting the DTC

D

The engine is running.

D

No MAP DTCs, or P0121, P0122, P0123 are set.

D

MAP reading is below 55 kPa.

D

Throttle is steady, throttle angle is changing less than
1%.

D

Predicted throttle angle is not close to actual throttle
angle.

D

Above conditions are present for a total of 12.5
seconds over a 25-second period of time.

Action Taken When the DTC Sets

D

The PCM will illuminate the malfunction indicator lamp
(MIL) after the second consecutive trip in which the
fault is detected.

D

The PCM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.

D

The PCM will use a default throttle position based on
mass air flow and RPM.

Conditions for Clearing the MIL/DTC

D

DTC P0121 can be cleared by using the Tech 2 “Clear
info ” function or by disconnecting the PCM battery
feed.

Diagnostic Aids

Check for the following conditions:

D

Skewed MAP signal or faulty Map sensor – An
incorrect MAP signal may cause the PCM to incorrectly
calculate the predicted TP sensor value during high
engine load situations.  Check for an unusually low
MAP reading.  This condition can cause DTC P0121 to
be set.

D

Poor connection at PCM – Inspect harness connectors
for backed-out terminals, improper mating, broken
locks improperly formed or damaged terminals, and
poor terminal-to-wire connection.

D

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–131

ENGINE DRIVEABILITY AND EMISSIONS

DTC P0121 –TP System Performance

 

Step

Action

Value(s)

Yes

No

1

Was the “On-Board Diagnostic (OBD) System Check”
performed?

—

Go to 

Step 2

Go to 

OBD

System

Check

2

1. Ignition “ON,” engine not running.
2. Observe the MAP reading on the Tech 2.

Is the MAP reading less than the specified value?

65 kPa

Go to 

Step 3

Go to 

Step 6

3

1. Disconnected the MAP sensor.
2. Connect a test light between the 5 volt reference “A”

circuit and the MAP signal circuit at the MAP sensor
harness connector.

3. Observe the MAP reading on the Tech 2.

Is the MAP reading less than the specified value?

65 kPa

Go to 

Step 5

Go to 

Step 4

4

1. Check the MAP signal circuit between the PCM and

the MAP sensor for an open, short to ground, or
short to the MAP ground circuit.

2. If the MAP signal circuit is open or shorted, repair it

as necessary.

Was the MAP signal circuit open or shorted?

—

Verify repair

Go to 

Step 12

5

Replace the MAP sensor.

Is the action complete?

—

Verify repair

—

6

Observe the TP angle reading on the Tech 2 while
slowly opening the throttle.

Does the TP 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 7

7

1. Disconnect the TP sensor.
2. Observe the TP sensor reading on the Tech 2.

Is the TP sensor reading near the specified value?

0 V

Go to 

Step 8

Go to 

Step 9

8

1. Connect a test light between the 5 volt reference “A”

circuit and the TP sensor signal circuit at the TP
sensor harness connector.

2. Observe the TP sensor reading on the Tech 2.

Is the TP sensor reading at the specified value?

5 V

Go to 

Step 11

Go to 

Step 10

9

Check the following items:

1. TP signal circuit for a short to voltage.
2. TP sensor ground circuit for high resistance

between the PCM and the TP sensor.

3. TP sensor ground circuit for a poor connection.
4. If a problem is found, repair wiring harness as

necessary.

Was a problem found?

—

Verify repair

Go to 

Step 12

6E–132

ENGINE DRIVEABILITY AND EMISSIONS

DTC P0121 –TP System Performance

  (Cont'd)

Step

No

Yes

Value(s)

Action

10

Check the following items:

1. TP signal circuit or 5 volt reference “A” circuit for a

poor connection.

2. TP signal circuit or 5 volt reference “A” circuit for

high resistance between the PCM and the TP
sensor.

3. If a problem is found, repair wiring harness as

necessary.

Was a problem found?

—

Verify repair

Go to 

Step 12

11

Replace the TP sensor.

Is the action complete?

—

Verify repair

—

12

Replace the PCM.

IMPORTANT: The replacement PCM must be
programmed.  Refer to 

UBS 98model year Immobilizer

Workshop Manual.

Is the action complete?

—

Verify repair

—