Page 4744 of 6000

6E–87 ENGINE DRIVEABILITY AND EMISSIONS
Fuel System Electrical Test
StepNo Ye s Va l u e ( s ) Action
9Check for short or open between the PCM and the fuel
pump relay.
Was a problem found?
—Verify repairGo to Step 10
101. Check the fuel pump relay circuit for a poor terminal
connection at the PCM.
2. If a problem is found, replace terminal as necessary.
Was a problem found?
—Verify repairGo to Step 11
11Replace the PCM.
IMPORTANT:The replacement PCM must be
programmed. Refer to
UBS 98model year Immobilizer
Workshop Manual.
Is the action complete?—Verify repair—
121. Reconnect the fuel pump relay.
2. Disconnect the fuel pump electrical connector at the
fuel tank.
3. Using a test light connected to ground, probe the
fuel pump feed wire (harness side).
4. Command the fuel pump “ON” with Tech 2.
Did the light illuminate for 2 seconds?
—Go to Step 15Go to Step 13
131. Honk the horn to verify that the horn relay is
functioning.
2. Substitute the horn relay for the fuel pump relay.
3. Leave the test light connected as in step 12.
4. Command the fuel pump “ON” with Tech 2.
Did the test light illuminate for 2 seconds when the fuel
pump was commanded “ON?”
—Go to Step 17Go to Step 14
141. Re-connect the horn relay in its proper location.
2. Check for a short circuit, blown fuse or open circuit
between the relay and the fuel tank.
Is the action complete?
—Verify repair—
151. With the fuel pump electrical connector at the fuel
tank disconnected, connect a test light between the
feed wire and the ground wire (harness side).
2. Command the fuel pump “ON” with Tech 2.
Did the test light illuminate for 2 seconds?
—Go to Step 18Go to Step 16
16Repair the open circuit in the fuel pump ground wire.
Is the action complete?
—Verify repair—
171. Re-connect the horn relay in its proper location.
2. Replace the fuel pump relay.
Is the action complete?
—Verify repair—
18Replace the fuel pump.
Is the action complete?
—Verify repair—
Page 4753 of 6000

6E–96
ENGINE DRIVEABILITY AND EMISSIONS
Knock Sensor (KS) System Check
(Engine Knock, Poor Performance, or Poor Economy)
StepActionVa l u e ( s )Ye sNo
1Is DTC P0325 or P0327 set?
—
Go to DTC
P0325 or
DTC P0327
Go to Step 2
2Run the engine at 1500 RPM.
Is there an internal engine knock?
—Go to Step 3Go to Step 4
3Repair the mechanical problem.
Is the action complete?
—Verify repair—
41. Install Tech 2.
2. Turn the ignition “ON.”
3. Cycle through the list until “Knock Retard” is
displayed.
Is knock retard at the specified value?
0Go to Step 6Go to Step 7
5Replace the PCM.
IMPORTANT:The replacement PCM must be
programmed. Refer to
UBS 98model year Immobilizer
Workshop Manual.
Is the action complete?—Verify repair—
61. Start the engine.
2. Monitor the knock retard display on Tech 2 while
changing the throttle setting to place different loads
on the engine.
Is knock retard at the specified value? (Turn the ignition
“OFF.”)
0Go to Step 9Go to Step 7
71. At the rear of the engine, behind the rear fuel
injector on the lift side, disconnect the 2-wire knock
sensor harness connector.
2. Attach the positive lead of DVM to B+.
3. On the m ain harness side of the connector, use th e
negative lead of the DVM to probe the connector pin
that is connected to the black wire.
Dose the DVM indicate the specified value?
(Reconnect the knock sensor harness.)
B+Go to Step 9Go to Step 8
8Repair the open black wire ground for the shield which
prevents stray electromagnetic pulses from affecting
the knock signal.
Is the action complete?
—Verify repair—
91. Reconnect the wire harness.
2. Set a DVM to AC voltage.
3. With the DVM, backprobe the PCM connector at
A2.
4. Tap the engine lift brackprobe with a socket
extension.
Did the DVM show an increase in AC voltage while
tapping on the lift bracket?
—System OKGo to Step 10
10Replace the knock sensor.
Is the action complete?
—Verify repair—
Page 4766 of 6000

6E–109 ENGINE DRIVEABILITY AND EMISSIONS
DTC P0102 – MAF Sensor Circuit Low Frequency
StepNo Ye s Va l u e ( s ) Action
91. Ignition “OFF.”
2. Disconnect the PCM white connector.
3. Ignition “ON.”
4. Check the MAF sensor signal circuit for a short to 5
volts.
Is the action complete?
—Verify repair—
101. Ignition “OFF.”
2. Disconnect the PCM white connector.
3. Ignition “ON.”
4. Check the MAF sensor signal circuit between the
PCM and the MAF sensor for an open, short to
ground, or short to the MAF ground circuit.
Is the action complete?
—Verify repairGo to Step 13
11Locate and repair the open in the ground circuit to the
MAF sensor.
Is the action complete?
—Verify repair—
12Locate and repair the open in the ignition feed circuit to
the MAF sensor.
Is the action complete?
—Verify repair—
13Replace the MAF sensor.
Is the action complete?
—Verify repairGo to Step 14
14Replace the PCM.
IMPORTANT:The replacement PCM must be
programmed. Refer to
UBS 98model year Immobilizer
Workshop Manual.
Is the action complete?—Verify repair—
Page 4768 of 6000

6E–111 ENGINE DRIVEABILITY AND EMISSIONS
DTC P0103 – MAF Sensor Circuit High Frequency
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. Review and record Tech 2 Failure Records data.
3. Operate the vehicle within Failure Records
conditions as noted.
4. Using a Tech 2, monitor “DTC” info for DTC P0103.
Does the Tech 2 indicate DTC P0103 failed this
ignition?
—Go to Step 3
Refer to
Diagnostic
Aids
31. Start the engine.
2. With the engine idling, monitor “MAF Frequency”
display on the Tech 2.
Is “MAF Frequency” above the specified value?
219 g/SecGo to Step 4Go to Step 7
41. Ignition “OFF.”
2. Disconnect the MAF sensor connector.
3. Ignition “ON,” engine idling.
4. Using a Tech 2, monitor “MAF Frequency.”
Does the Tech 2 indicate a “MAF Frequency” at the
specified value?
0.0 g/SecGo to Step 5Go to Step 6
5Replace the MAF sensor.
Is the action complete?
—Verify repairGo to Step 8
61. Check the MAF harness for incorrect routing near
high voltage components (solenoids, relays,
motors).
2. If incorrect routing is found, correct the harness
routing.
Was a problem found?
—Verify repairGo to Step 7
71. With the engine idling, monitor “MAF Frequency”
display on the Tech 2.
2. Quickly snap open throttle to wide open throttle
while under a road load and record value.
Does the Tech 2 indicate “MAF Frequency” above the
specified value?
219 g/SecGo to Step 5Go to Step 8
8Replace the PCM.
IMPORTANT:The replacement PCM must be
programmed. Refer to
UBS 98model year Immobilizer
Workshop Manual.
Is the action complete?—Verify repair—
Page 4771 of 6000
6E–114
ENGINE DRIVEABILITY AND EMISSIONS
DTC P0107 – MAP Sensor Circuit Low Voltage
StepNo Ye s Va l u e ( s ) Action
9Check the MAP sensor signal circuit for a poor
connection at the PCM and the MAP sensor; replace
the terminal if necessary.
Did the terminal require replacement?
—Verify repairGo to Step 11
10Replace the MAP sensor.
Is the action complete?
—Verify repair—
11Replace the PCM.
IMPORTANT:The replacement PCM must be
programmed. Refer to
UBS 98model year Immobilizer
Workshop Manual.
Is the action complete?—Verify repair—
Page 4774 of 6000
6E–117 ENGINE DRIVEABILITY AND EMISSIONS
DTC P0108 – MAP Sensor Circuit High Voltage
StepNo Ye s Va l u e ( s ) Action
11Replace the PCM.
IMPORTANT:The replacement PCM must be
programmed. Refer to
UBS 98model year Immobilizer
Workshop Manual.
Is the action complete?—Verify Repair—
12Replace the MAP sensor.
Is the action complete?
—Verify repair—
Page 4777 of 6000

6E–120
ENGINE DRIVEABILITY AND EMISSIONS
DTC P0112–IAT Sensor Circuit 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
21. Ignition “ON,” engine “OFF.”
2. Using a Tech 2, monitor the intake air temperature
(IAT).
Is the intake air temperature greater than the specified
value?
148C
(283
F)Go to Step 4Go to Step 3
31. 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 the “Specific DTC” info for
DTC P0112.
Does the Tech 2 indicate DTC P0112 failed this
ignition?
—
Refer to Te s t
Description
Refer to
Diagnostic
Aids
41. Ignition “OFF.”
2. Disconnect the IAT sensor electrical connector.
3. Ignition “ON.”
4. Observe the intake air temperature on the Tech 2.
Is the intake air temperature below the specified value?
–38C
(–36
F)Go to Step 6Go to Step 5
51. Ignition “OFF.”
2. Disconnect the PCM electrical connectors.
3. Check the IAT sensor signal circuit for a short to
ground.
Is the IAT sensor signal circuit shorted to ground?
—Verify repairGo to Step 7
6Replace the IAT sensor.
Is the action complete?
—Verify repair—
7Replace the PCM.
IMPORTANT:The replacement PCM must be
programmed. Refer to
UBS 98model year Immobilizer
Workshop Manual.
Is the action complete?—Verify repair—
Page 4780 of 6000

6E–123 ENGINE DRIVEABILITY AND EMISSIONS
DTC P0113 –IAT Sensor Circuit High Voltage
StepNo Ye s Va l u e ( s ) Action
6Check for poor connections at the IAT sensor and
replace terminals if necessary.
Did any terminals require replacement?
—Verify repairGo to Step 10
71. Ignition “OFF.”
2. Disconnect the PCM, and check the IAT sensor
ground circuit for an open.
3. If the IAT sensor ground circuit is open, repair it as
necessary.
Was the IAT sensor ground circuit open?
—Verify repairGo to Step 9
81. Ignition “OFF.”
2. Disconnect the PCM, and check the IAT signal
circuit for an open.
3. If the IAT sensor signal circuit is open, repair it as
necessary.
Was the IAT signal circuit open?
—Verify repairGo to Step 9
9Check for a poor sensor ground or IAT signal circuit
terminal connection at the PCM and replace
terminal(s) if necessary.
Did any of the terminals need to be replaced?
—Verify repairGo to Step 11
10Replace the IAT sensor.
Is the action complete?
—Verify repair—
11Replace the PCM.
IMPORTANT:The replacement PCM must be
programmed. Refer to
UBS 98model year Immobilizer
Workshop Manual.
Is the action complete?—Verify repair—