Opel Frontera UBS. Manual - part 286

 

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Opel Frontera UBS. Manual - part 286

 

 

6E–50

ENGINE DRIVEABILITY AND EMISSIONS

Primary System-Based Diagnostic

Primary System-Based Diagnostic

There are primary system-based diagnostics which
evaluate system operation and its effect on vehicle
emissions.  The primary system-based diagnostics are
listed below with a brief description of the diagnostic
function:

Oxygen Sensor Diagnosis
The fuel control heated oxygen sensors (Bank 1 HO2S 1
and Bank 2 HO2S 1) are diagnosed for the following
conditions:

D

Inactive signal (output steady at bias voltage – approx.
450 mV)

D

Signal fixed high

D

Signal fixed low

If the oxygen sensor pigtail wiring, connector or terminal
are damaged, the entire oxygen sensor assembly must
be replaced.  DO NOT attempt to repair the wiring,
connector or terminals.  In order for the sensor to function
properly, it must have clean reference air provided to it.
This clean air reference is obtained by way of the oxygen
sensor wire(s).  Any attempt to repair the wires, connector
or terminals could result in the obstruction of the
reference air and degrade oxygen sensor performance.
Refer to 

On-Vehicle Service, Heated Oxygen Sensors.

Fuel Control Heated Oxygen Sensor

The main function of the fuel control heated oxygen
sensors is to provide the control module with exhaust
stream oxygen content information to allow proper fueling
and maintain emissions within mandated levels.  After it
reaches operating temperature, the sensor will generate
a voltage, inversely proportional to the amount of oxygen
present in the exhaust gases.  The control module uses
the signal voltage from the fuel control heated oxygen
sensors while in closed loop to adjust fuel injector pulse
width.  While in closed loop, the PCM can adjust fuel
delivery to maintain an air/fuel ratio which allows the best
combination of emission control and driveability.

HO2S Heater

Heated oxygen sensors are used to minimize the amount
of time required for closed loop fuel control to begin
operation and to allow accurate catalyst monitoring.  The
oxygen sensor heater greatly decreases the amount of
time required for fuel control sensors (Bank 1 HO2S 1 and
Bank2 HO2S 1) to become active.  Oxygen sensor
heaters are required to maintain a sufficiently high
temperature which allows accurate exhaust oxygen
content readings further away from the engine.

Fuel Trim System Monitor Diagnostic

Operation

Fuel Trim System Monitor Diagnostic
Operation

This system monitors the averages of short-term and
long-term fuel trim values.  If these fuel trim values stay at
their limits for a calibrated period of time, a malfunction is
indicated.  The fuel trim diagnostic compares the
averages of short-term fuel trim values and long-term fuel
trim values to rich and lean thresholds.  If either value is
within the thresholds, a pass is recorded.  If both values
are outside their thresholds, a rich or lean DTC will be
recorded.
The fuel trim system diagnostic also conducts an intrusive
test.  This test determines if a rich condition is being
caused by excessive fuel vapor from the EVAP canister.
In order to meet OBD requirements, the control module
uses weighted fuel trim cells to determine the need to set
a fuel trim DTC.  A fuel trim DTC can only be set if fuel trim
counts in the weighted fuel trim cells exceed
specifications.  This means that the vehicle could have a
fuel trim problem which is causing a problem under
certain conditions (i.e., engine idle high due to a small
vacuum leak or rough idle due to a large vacuum leak)
while it operates fine at other times.  No fuel trim DTC
would set (although an engine idle speed DTC or HO2S
DTC may set).  Use a Tech 2 to observe fuel trim counts
while the problem is occurring.
A fuel trim DTC may be triggered by a number of vehicle
faults.  Make use of all information available (other DTCs
stored, rich or lean condition, etc.) when diagnosing a fuel
trim fault.

Fuel Trim Cell Diagnostic Weights

No fuel trim DTC will set regardless of the fuel trim counts
in cell 0 unless the fuel trim counts in the weighted cells
are also outside specifications.  This means that the
vehicle could have a fuel trim problem which is causing a
problem under certain conditions (i.e. engine idle high due
to a small vacuum leak or rough due to a large vacuum
leak) while it operates fine at other times.  No fuel trim
DTC would set (although an engine idle speed DTC or
HO2S DTC may set).  Use a Tech 2 to observe fuel trim
counts while the problem is occurring.

6E–51

ENGINE DRIVEABILITY AND EMISSIONS

On-Board Diagnostic (OBD) System Check

TS321119

Circuit Description

The on-board diagnostic system check is the starting
point for any driveability complaint diagnosis.  Before
using this procedure, perform a careful visual/physical
check of the PCM and engine grounds for cleanliness and
tightness.
The on-board diagnostic system check is an organized
approach to identifying a problem created by an
electronic engine control system malfunction.

Diagnostic Aids

An intermittent may be caused by a poor connection,
rubbed-through wire insulation or a wire broken inside the
insulation.  Check for poor connections or a damaged
harness.  Inspect the PCM harness and connector for
improper mating, broken locks, improperly formed or
damaged terminals, poor terminal-to-wire connection,
and damaged harness.

Test Description

Number(s) below refer to the step number(s) on the
Diagnostic Chart:
1. The MIL (“Check Engine” lamp) should be “ON”

steady with the ignition “ON”/engine “OFF.”  If not,
Chart A-1 should be used to isolate the malfunction.

2. Checks the Class 2 data circuit and ensures that the

PCM is able to transmit serial data.

3. This test ensures that the PCM is capable of

controlling the MIL (“Check Engine” lamp) and the
MIL (“Check Engine” lamp) driver circuit is not
shorted to ground.

4. If the engine will not start, the 

Cranks But Will Not

Run chart should be used to diagnose the condition.

7. A Tech 2 parameter which is not within the typical

range may help to isolate the area which is causing
the problem.

6E–52

ENGINE DRIVEABILITY AND EMISSIONS

10.This vehicle is equipped with a PCM which utilizes

an electrically erasable programmable read only
memory (EEPROM).  When the PCM is replaced,
the new PCM must be programmed. 

Refer to UBS

98 model year Immobilizer Workshop Manual.

6E–53

ENGINE DRIVEABILITY AND EMISSIONS

On-Board Diagnostic (OBD) System Check

 

Step

Action

Value(s)

Yes

No

1

1. Ignition “ON,” engine “OFF.”
2. Observe the malfunction indicator lamp (MIL or

“Check Engine” lamp). 

Is the MIL (“Check Engine” lamp)“ON?”

Go to 

Step 2

Go to 

No MIL

(“Check

Engine” lamp)

2

1. Ignition “OFF.”
2. Install a Tech 2.
3. Ignition “ON.”
4. Attempt to display PCM engine data with the Tech 2.

Does the Tech 2 display PCM data?

Go to 

Step 3

Go to 

Step 8

3

1. Using the Tech 2 output tests function, select MIL

(“Check Engine” lamp) dash lamp control and
command the MIL (“Check Engine” lamp) “OFF.”

2. Observe the MIL (“Check Engine” lamp).

Did the MIL (“Check Engine” lamp) turn “OFF?”

Go to 

Step 4

Go to 

MIL

(“Check

Engine” lamp)

On Steady

4

Attempt to start the engine.

Did the engine start and continue to run?

Go to 

Step 5

Go to 

Cranks

But Will Not

Run

5

Select “Display DTCs” with the Tech 2.

Are any DTCs stored?

Go to 

Step 6

Go to 

Step 7

6

Are two or more of the following DTCs stored?  P0107,
P0108, P0113, P0118, P0122, P0123, P0712.?

Go to

“Multiple

PCM

Information

Sensor DTCs

Set”

Go to

applicable
DTC table

7

Compare PCM data values displayed on the Tech 2 to
the typical engine scan data values.

Are the displayed values normal or close to the typical
values?

Refer

to

Typical

scan data

value

Refer to

indicated

Component

System
Checks

8

1. Ignition “OFF,” disconnect the PCM.
2. Ignition “ON,” engine “OFF.”
3. Check the Class 2 data circuit for an open, short  to

ground, or short to voltage.  Also, check the DLC
ignition feed circuit for an open or short to ground
and the DLC ground circuit for an open.

4. If a problem is found, repair as necessary.

Was a problem found?

Go to 

Step 2

Go to 

Step 9

9

Attempt to display PCM data with the Tech 2.

Does the Tech 2 display PCM engine data?

Go to 

Step 2

Go to 

Step 10

10

Replace the PCM.

IMPORTANT: The replacement PCM must be
programmed. Refer to 

Powertrain Control Module

(PCM) in On-Vehicle Service.

Is the action complete?

Go to 

Step 2

 

 

 

 

 

 

 

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