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Opel Frontera UBS. Manual - part 336

6E–250

ENGINE DRIVEABILITY AND EMISSIONS

DTC P1404 – EGR Closed Stuck

Step

Action

Value(s)

Yes

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

—

Go to

Step 2

Go to

OBD

System

Check

1. Ignition “ON,” engine “OFF”, review and record

Tech 2 Failure Records Data.

2. Operate the vehicle within Failure Records

conditions as noted.

3. Using a Tech 2, monitor “DTC inf. for DTC P1404

until the DTC P1404 test runs. Note the result.

Does the Tech 2 indicates DTC P1404 failed this
ignition?

—

Go to

Step 3

Refer to

Diagnostic

Aids

1. Disconnect the EGR valve harness connector.
2. Inspect the EGR valve and connectors for damaged

pin or terminals.

Were there any damaged pins or terminals?

—

Go to

Step 4

Go to

Step 5

Repair the damaged pin or terminal.

Is the action complete?

—

Verify repair

—

1. Remove EGR valve from Engine.
2. Inspect EGR valve whether there is any excessive

carbon deposit on EGR shaft.

3. Inspect any foreign material inside of EGR valve.

Was excessive carbon deposit on EGR valve shaft
or/and foreign material in EGR valve ?

—

Go to

Step 6

Go to

Step 7

1. Clean up EGR valve shaft and inside of EGR valve.
2. Remove foreign material from EGR valve.
3. Visually inspect damage of pintle and seat whether

there is bent, leakage may occur.

Was there any severe damage which affects function?

3–6 ohms

Go to

Step 8

Verify repair

Go to

Step 7

1. Reconnect.
2. Ignition “OFF”.
3. Install the Tech 2.
4. Run the engine at idle.
5. On the Tech 2, select F3:Misc. Test F5:EGR.
6. Use the “UP” arrow to increase the EGR from 0% to

40%.

Did EGR work properly?

—

Go to

Step 8

1. Reset the learned zero EGR valve position.
2. Repeat step 7.

Did EGR work properly?

—

Verify repair

Go to

Step 9

Replace the EGR valve.

Replace the EGR valve. Does DTC P1404 still fail
“specific DTC” test on the Tech 2?

—

Go to

Step 10

Verify repair

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–251

ENGINE DRIVEABILITY AND EMISSIONS

Diagnostic Trouble Code (DTC) P1508 IAC System Low RPM

T321115

Circuit Description

The powertrain control module (PCM) controls engine
idle speed by adjusting the position of the idle air control
(IAC) motor pintle. The IAC is a bi-directional stepper
motor driven by two coils. The PCM applies current to the
IAC coils in steps (counts) to extend the IAC pintle into a
passage in the throttle body to decrease air flow. The
PCM reverses the current to retract the pintle, increasing
air flow. This method allows highly accurate control of idle
speed and quick response to changes in engine load. If
the PCM detects a condition where too low of an idle
speed is present and the PCM is unable to adjust idle
speed by increasing the IAC counts, DTC P1508 will set,
indicating a problem with the idle control system.

Conditions for Setting the DTC

No Tech 2 test is being run.

None of these DTCs are set: TP sensor, VSS, ECT,
EGR, fuel system, MAF, MAP, IAT, canister purge,
injector control or ignition control.

Barometric pressure is above 75 kPa.

Engine coolant temperature (ECT) is above 50

(120

F).

Engine speed is more than 100-200 RPM lower than
desired idle, based upon coolant temperature.

The engine has been running for at least 125 seconds.

Vehicle speed is less than 1 mph.

Canister purge duty cycle is above 10%.

Ignition voltage is between 9.5 volts and 16.7 volts.

The throttle is closed.

Engine speed is lower than desired idle.

All of the above conditions are met for 10 seconds.

Action Taken When the DTC Sets

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

The PCM 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 P1508 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:

Poor connection at PCM or IAC motor – 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 for damage.

Restricted air intake system – Check for a possible
collapsed air intake duct, restricted air filter element,
or foreign objects blocking the air intake system.

Throttle body – Check for objects blocking the IAC
passage or throttle bore, excessive deposits in the IAC

6E–252

ENGINE DRIVEABILITY AND EMISSIONS

passage and on the IAC pintle, and excessive deposits
in the throttle bore and on the throttle plate.

Large vacuum leak – Check for a condition that causes
a large vacuum leak, such as an incorrectly installed or
faulty PCV valve or a disconnected brake booster
hose.

Reviewing the Failure Records vehicle mileage since the
diagnostic test last failed may help determine how often
the condition that caused the DTC to be set occurs. This
may assist in diagnosing the condition.

DTC P1508 – IAC System Low RPM

Step

Action

Value(s)

Yes

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

—

Go to

Step 2

Go to

OBD

System

Check

1. Start the engine.
2. Turn all accessories “OFF”(A/C, rear defroster,

etc).

3. Using a Tech 2, command RPM up to 1500, down to

500, and the up to 1500 while monitoring the
“Engine Speed” on the Tech 2.

NOTE: This Tech 2 command may cause the engine to
“cut out” when RPM goes above 1500. If this occurs,
the “cutting out” will stop when the Tech 2 command for
the test is discontinued, or if the Tech 2 command is
changed to less than 1500 RPM.

Does the “Engine Speed” remain within the specified
value of the “Desired Idle” for each RPM command?

50 RPM

No trouble

found. Go to

Diagnostic

Aids

Go to

Step 3

1. Disconnect the IAC.
2. Install IAC Node Light 5-8840-2312-0 or equivalent.
3. With the engine running, command RPM up to

1500, down to 500, and then up to 1500 while
observing the node light.

Does each node light cycle red and green (never
“OFF”)?

—

Go to

Step 5

Go to

Step 4

1. Check the following circuits for an open, short to

voltage, short ground, or poor connections at the
PCM:

IAC “A” Low.

IAC “A” High.

IAC “B” Low.

IAC “B” High.

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

Was a problem found?

—

Verify repair

Go to

Step 8

6E–253

ENGINE DRIVEABILITY AND EMISSIONS

DTC P1508 – IAC System Low RPM

(Cont'd)

Step

Yes

Value(s)

Action

Visually/physically inspect for following conditions:

Restricted air intake system. Check for a possible
collapsed air intake duct, restricted air filter
element, or foreign objects blocking the air intake
system.

Throttle body. Check for objects blocking the IAC
passage or throttle bore, excessive deposits in
the IAC passage and on the IAC pintle, and
excessive deposits in the throttle bore and on the
throttle plate.

Do any of the above require a repair?

—

Refer to

appropriate

section for

on-vehicle

service

Go to

Step 6

1. Check for a poor connection at the IAC harness

connector.

2. If a problem is found, replace faulty terminals as

necessary.

Was a problem found?

—

Verify repair

Go to

Step 7

Replace the IAC valve.

Is the action complete?

—

Verify repair

—

Replace the PCM.

IMPORTANT: The replacement PCM must be
programmed. Refer to

UBS 98model year Immobilizer

Workshop Manual.

Is the action complete?

—

Verify repair

—

Content .. 334 335 336 337 ..