Opel Frontera UE. Manual - part 799

6E1–79

X22SE 2.2L ENGINE DRIVEABILITY AND EMISSION

Fuel System Diagnosis

  (Cont'd)

Step

No

Yes

Value(s)

Action

10

Locate and repair the loss of vacuum to the fuel
pressure regulator.

Is the action complete?

—

Verify repair

—

11

Replace the fuel pressure regulator.

Is the action complete?

—

Verify repair

—

12

1. Run the fuel pump with the Tech 2.
2. After pressure has built up, turn off the pump and

clamp the supply hose shut with suitable locking
pliers which will not damage the hose.

Does the fuel pressure indicated by the fuel pressure
gauge remain constant?

—

Go to Step 13

Go to Step 15

13

Visually inspect the fuel supply line and repair any
leaks.

Was a problem found?

—

Verify repair

Go to Step 14

14

Remove the fuel tank and inspect for leaky hose or
in–tank fuel line.

Was a problem found?

—

Verify repair

Go to Step 8 

15

1. If the pliers are still clamped to the fuel supply hose,

remove the locking pliers.

2. With suitable locking pliers which will not damage

the hose, clamp the fuel return line to prevent fuel
from returning to the fuel tank.

3. Run the fuel pump with the Tech 2.
4. After pressure has built up, remove power to the

pump.

Does the fuel pressure indicated by the fuel pressure
gauge remain constant?

—

Go to Step 11

Go to Step 16

16

Locate and replace any leaking fuel injector(s).

Is the action complete?

—

Verify repair

—

17

Is the fuel pressure indicated by the fuel pressure
gauge above the specified limit?

376 kPa  (55

psi)

Go to Step 18

Go to Step 21

18

1. Relieve the fuel pressure. Refer to the Fuel

Pressure Relief. 

2. Disconnect the fuel return line from the fuel rail.
3. Attach a length of flexible hose to the fuel rail return

outlet passage.

4. Place the open end of the flexible hose into an

approved gasoline container.

5. Run the fuel pump with the Tech 2.
6. Observe the fuel pressure indicated by the fuel

pressure gauge with the fuel pump running.

Is the fuel pressure within the specified limits?

290–376 kPa

(42–55 psi)

Go to Step 19

Go to Step 20

19

Locate and correct the restriction in the fuel return line.

Is the action complete?

—

Verify repair

—

20

Visually and physically inspect the fuel rail outlet
passages for a restriction.

Was a restriction found?

—

Verify repair

Go to Step 11

6E1–80

X22SE 2.2L ENGINE DRIVEABILITY AND EMISSION

Fuel System Diagnosis

  (Cont'd)

Step

No

Yes

Value(s)

Action

21

Is the fuel pressure indicated by the fuel pressure
gauge above the specified value?

0 kPa (0 psi)

Go to Step 22

Go to Step 23

22

1. Command the fuel pump ON with the Tech 2.
2. Using suitable pliers which will not damage the fuel

hose, gradually apply pressure with the pliers to
pinch the flexible fuel return hose closed.

CAUTION: Do not let the fuel pressure exceed
the second specified value.

Does the fuel pressure indicated by the fuel pressure
gauge rise above the first specified value?

414 kPa (60

psi)

Go to Step 11

Go to Step 7 

23

1. Command the fuel pump ON with the Tech 2.
2. Remove the fuel filler cap and listen for the sound of

the fuel pump running.

3. Turn the pump off.

Was the fuel pump running?

—

Go to Step 7 

Go to Fuel

System

Electrical Test

Chart 

6E1–81

X22SE 2.2L ENGINE DRIVEABILITY AND EMISSION

IDLE AIR CONTROL (IAC) SYSTEM CHECK

D06RX112

Circuit Description

The engine control module (ECM) controls engine idle
speed with the idle air control (IAC) valve. To increase idle
speed, the ECM retracts the IAC valve pintle away from
its seat, allowing more air to bypass the throttle bore. To
decrease idle speed, it extends the IAC valve pintle
towards its seat, reducing bypass air flow. A Tech 2 will
read the ECM commands to the IAC valve in counts.
Higher counts indicate more air bypass (higher idle).
Lower counts indicate less air is allowed to bypass (lower
idle).

Diagnostic Aids

A slow, unstable, or fast idle may be caused by a non-IAC
system problem that cannot be overcome by the IAC
valve.  Out of control range IAC Tech 2 counts will be

above 60 if idle is too low, and zero counts if idle is too
high.  The following checks should be made to repair a
non-IAC system problem:

D

Vacuum leak (high idle) – If idle is too high, stop the
engine.  Fully extend (low) IAC with the Tech 2.  Start
the engine.  If idle speed is above 800 RPM, locate
and correct the vacuum leak, including the PCV
system.  Check for binding of the throttle blade or
linkage.

D

Lean heated oxygen sensor signal (high air/fuel ratio)
– The idle speed may be too high or too low.  Engine
speed may vary up and down, and disconnecting the
IAC valve does not help.  Diagnostic trouble codes
P0131, P0151, P0171, may be set.  Tech 2 oxygen
(O2) voltage will be less than 100 mV (0.1 V).  Check
for low regulated fuel pressure, water in fuel, or a
restricted injector.

6E1–82

X22SE 2.2L ENGINE DRIVEABILITY AND EMISSION

D

Rich heated oxygen sensor signal (low air/fuel ratio) –
The idle speed will be too low.  Tech 2 IAC counts will
usually be above 80.  The system is obviously rich
and may exhibit black smoke in the exhaust.
Tech 2 O2 voltage will be fixed at about 750 mV (0.75
V).  Check for high fuel pressure, or a leaking or
sticking injector.  A silicon-contaminated heated
oxygen sensor will show an O2 voltage slow to
respond on Tech 2.

D

Throttle body – Remove the IAC valve and inspect the
bore for foreign material.

D

IAC valve electrical connections – IAC valve
connections should be carefully checked for proper
contact.

D

PCV valve – An incorrect or faulty PCV valve may
result in an incorrect idle speed.  Refer to 

Diagnosis,

Rough Idle, Stalling.  If intermittent poor driveability or
idle symptoms are resolved by disconnecting the
IAC, carefully recheck the connections and valve
terminal resistance, or replace the IAC.

Test Description

Number(s) below refer to the step number(s) on the
Diagnostic Chart.
1. The Tech 2 is used to extend and retract the IAC

valve.  Valve movement is verified by an engine
speed change.  If no change in engine speed
occurs, the valve can be resettled when removed
from the throttle body.

2. This step checks the quality of the IAC movement in

step 1.  Between 700 revolutions per minute (RPM)
and about 1500 RPM, the engine speed should
change smoothly with each flash of the tester light
in both extend and retract.  If the IAC valve is
retracted beyond the control range (about 1500
RPM), it may take many flashes to extend the IAC
valve before engine speed will begin to drop.  This
is normal on certain engines.  Fully extending the
IAC may cause engine stall.  This may be normal.

Idle Air Control (IAC) System Check

 

Step

Action

Value(s)

Yes

No

1

1. Ignition “OFF.”
2. Connect the Tech 2.
3. Set the parking brake.
4. Block the wheels.
5. Turn the air conditioning “OFF.”
6. Idle the engine in Park (A/T) or Neutral (M/T).
7. Operate the IAC test.
8. The engine speed should decrease and increase as

the IAC is cycled.

Does the RPM change?

—

Go to 

Step 2

Go to 

Step 3

2

RPM should change smoothly.

Does the RPM change within the range specified?

700-1500

RPM

—

Go to 

Step 3

3

Check the IAC passages.

Are the IAC passages OK?

—

Go to 

Step 4

Go to 

Step 5

4

Clear any obstruction from the IAC passages.

Is the action complete?

—

Verify repair

—

5

Replace the IAC.  Refer to 

On-Vehicle Service, Idle Air

Control Valve.

Is the action complete?

—

Verify repair

—