TEST ACTION APPLICABILITY
2 Ignition on, engine not running
With the DRB, read DTCs and Freeze Frame Data and record.
With the DRB, Clear DTCs.
Start the engine and allow the engine to idle.
With the DRB, perform the LDP Monitor test.
Wiggle the wiring harness and connectors from the LDP connector to the PCM
connector while the monitor is running.
Note: Be careful of the engine's moving parts.
With the DRB, Read DTCs.
Does the P-1494 Leak Detection Pump Sw or Mechanical Fault DTC return during
the wiggle test?All
Ye s®Repair the wiring harness or connector as necessary.
Perform Powertrain Verification Test VER-5A.
No®Go To 3
3 Ignition Off
Using the schematic as a guide, inspect the Wiring and Connectors.
Were any problems found?All
Ye s®Repair as necessary.
Perform Powertrain Verification Test VER-5A.
No®Test Complete.
4 Ignition Off
Disconnect the LDP Connector.
Note: Check connectors - Clean/repair as necessary.
Engine off, key on.
Using a voltmeter, probe the Fused Ignition Switch Output Circuit.
Is the voltage above 10.0 volts?All
Ye s®Go To 5
No®Repair the open Fused Ignition Switch Output Circuit.
Perform Powertrain Verification Test VER-5A.
5 Ignition Off
Disconnect the Engine Vacuum Supply Hose at the LDP.
Install a Vacuum Gauge to Engine Vacuum Supply Hose at the LDP.
Start engine and read Vacuum Gauge.
Does Vacuum Gauge read within 1 inch of engine vacuum?All
Ye s®Go To 6
No®Repair leak or obstruction in Vacuum Hose.
Perform Powertrain Verification Test VER-5A.
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DRIVEABILITY
P-1494 LEAK DETECTION PUMP PRESSURE SWITCH ÐContinued
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TEST ACTION APPLICABILITY
6 Ignition Off
Disconnect the LDP Connector.
Note: Check connectors - Clean/repair as necessary.
Disconnect the PCM.
Note: Check connectors - Clean/repair as necessary.
Using an Ohmmeter, measure the resistance of the LDP Pressure Switch Sense
Circuit from the PCM Connector to a good ground.
Is the resistance below 5.0 ohms?All
Ye s®Repair the LDP Pressure Switch Sense Circuit for a short to
ground.
Perform Powertrain Verification Test VER-5A.
No®Go To 7
7 Ignition Off
Disconnect the LDP Connector.
Note: Check connectors - Clean/repair as necessary.
Disconnect the PCM.
Note: Check connectors - Clean/repair as necessary.
Using an Ohmmeter, measure the resistance of the LDP Pressure Switch Sense
Circuit from the PCM Connector to the LDP Connector.
Is the resistance below 5.0 ohms?All
Ye s®Go To 8
No®Repair the open LDP Switch Sense Circuit.
Perform Powertrain Verification Test VER-5A.
8 Ignition Off
Disconnect the Engine Vacuum Supply Hose at the LDP.
Disconnect the PCM.
Note: Check connectors - Clean/repair as necessary.
Key on.
With voltmeter connected to LDP switch sense circuit at PCM connector, ground the
LDP solenoid control circuit. Then while applying vacuum to LDP with a hand
vacuum pump, observe voltmeter.
Did the voltage change?All
Ye s®Go To 9
No®Replace the LDP.
Perform Powertrain Verification Test VER-5A.
9 Ignition Off
If there are no potential causes remaining, the PCM is assumed to be defective.
View repair options.All
Repair
Replace the PCM.
Perform Powertrain Verification Test VER-5A.
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DRIVEABILITY
P-1494 LEAK DETECTION PUMP PRESSURE SWITCH ÐContinued
ProCarManuals.com
TEST ACTION APPLICABILITY
4 Check the freeze frame data to determine the conditions when code was set.
Attempt duplication of 'freeze frame' conditions for added diagnostics.
If there are no other possible causes remaining there is assumed to be an9intermit-
tent9problem with a Wiring Harness Connector or Wire.
View repair options.All
Repair
Visually inspect related Wire Harness Connectors and Harnesses.
Look for broken, bent, pushed out, or corroded terminals and for
chafed, pierced, or partiallly broken wire, respectively. Refer to
any hotlines or technical service bulletins that apply.
5 Ignition Off
Disconnect the LDP Solenoid.
Note: Check connectors - Clean/repair as necessary.
Key on.
Using a Voltmeter, measure the voltage of the Fused Ignition Switch Output Circuit
at the Solenoid Connector.
Is the voltage above 10.0 volts?All
Ye s®Go To 6
No®Repair the open Fused Ignition Switch Output Circuit.
Perform Powertrain Verification Test VER-6A.
6 Ignition Off
Disconnect the LDP Solenoid.
Note: Check connectors - Clean/repair as necessary.
Disconnect the PCM.
Note: Check connectors - Clean/repair as necessary.
Using an Ohmmeter, measure the resistance of the LDP Solenoid Control Circuit at
the PCM Connector to ground.
Is the resistance below 5.0 ohms?All
Ye s®Repair the LDP Solenoid Circuit for a short to ground.
Perform Powertrain Verification Test VER-6A.
No®Go To 7
7 Ignition Off
Disconnect the LDP Solenoid.
Note: Check connectors - Clean/repair as necessary.
Disconnect the PCM.
Note: Check connectors - Clean/repair as necessary.
With an Ohmmeter, measure the resistance of the LDP Solenoid Control Circuit from
the PCM Connector to the LDP Connector.
Is the resistance below 5.0 ohms?All
Ye s®Go To 8
No®Repair the open LDP Solenoid Control Circuit.
Perform Powertrain Verification Test VER-6A.
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DRIVEABILITY
P-1495 LEAK DETECTION PUMP SOLENOID CIRCUIT ÐContinued
ProCarManuals.com
TEST ACTION APPLICABILITY
8 Ignition Off
Disconnect the PCM.
Note: Check connectors - Clean/repair as necessary.
Key on.
With a Voltmeter, measure voltage of the LDP Solenoid Control Circuit at the PCM
Connector.
Is the voltage above 10.0 volts?All
Ye s®Go To 9
No®Replace the LDP.
Perform Powertrain Verification Test VER-6A.
9 If there are no potential causes remaining, the PCM is assumed to be defective.
View repair options.All
Repair
Replace the PCM.
Perform Powertrain Verification Test VER-6A.
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DRIVEABILITY
P-1495 LEAK DETECTION PUMP SOLENOID CIRCUIT ÐContinued
ProCarManuals.com
TEST ACTION APPLICABILITY
3 Ignition Off
Disconnect the PCM Connectors.
Disconnect the TCM Connector.
Note: Check connectors - Clean/repair as necessary.
Using an Ohmmeter, measure the CCD Bus (+) Circuit between the PCM and TCM
Connectors.
Is the resistance below 5.0 ohms?All
Ye s®Go To 4
No®Repair the open CCD Bus (+) Circuit between PCM and TCM.
Perform Powertrain Verification Test VER-2A.
4 Ignition Off
Disconnect the PCM Connectors.
Disconnect the TCM Connector.
Note: Check connectors - Clean/repair as necessary.
Using an Ohmmeter, measure the CCD Bus (-) Circuit between the PCM and TCM
Connectors.
Is the resistance below 5.0 ohms?All
Ye s®Go To 5
No®Repair the open CCD Bus (-) Circuit between the PCM and TCM.
Perform Powertrain Verification Test VER-2A.
5 Key On
Using the DRB under9Transmission9select941TE9.
Does the DRB display show9No Response9?All
Ye s®Replace the Transmission Control Module.
Perform Powertrain Verification Test VER-2A.
No®Go To 6
6 If there are no potential causes remaining, the Powertrain Control Module is
assumed to be defective.
View repair options.All
Repair
Replace the PCM.
Perform Powertrain Verification Test VER-2A.
7 Ignition Off
Using the schematic as a guide, inspect the Wiring and Connectors.
Were any problems found?All
Ye s®Repair as necessary.
Perform Powertrain Verification Test VER-2A.
No®Test Complete.
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DRIVEABILITY
P-1698 NO CCD MESSAGES FROM TCM ÐContinued
ProCarManuals.com
TEST ACTION APPLICABILITY
18 Ignition Off
Inspect the Chassis Fuel Supply Line to engine for a kink or restriction.
Is the Fuel Line kinked or restricted?ENGINE - 3.0L V6
Ye s®Release the Fuel Pressure. Repair the Fuel Line as necessary.
Perform Powertrain Verification Test VER-2A.
No®Go To 19
19 Ignition Off
Warning: The Fuel System must be opened and may be under high pressure.
Release the fuel pressure.
Install Fuel Pressure Gauge between Fuel Tank and Fuel Filter.
Key on.
With the DRB, actuate the ASD Fuel System test.
Is fuel pressure at least 5 psi higher than the previously recorded pressure?ENGINE - 3.0L V6
Ye s®Release the Fuel Pressure. Replace the Fuel Filter.
Perform Powertrain Verification Test VER-2A.
No®Go To 20
20 Ignition Off
Warning: The Fuel System must be opened and may be under high pressure.
Release the fuel pressure.
Install Fuel Pressure Gauge between Fuel Tank and Fuel Filter.
Key on.
With the DRB, actuate the ASD Fuel System test.
Is fuel pressure at least 5 psi higher than the previously recorded pressure?ENGINE - 3.0L V6
Ye s®Test Complete.
No®Release the Fuel Pressure. Replace the Fuel Pump and Regulator
Assembly.
Perform Powertrain Verification Test VER-2A.
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DRIVEABILITY
* CHECKING FUEL DELIVERY ÐContinued
ProCarManuals.com
Symptom:
* CHECKING OXYGEN SENSOR HEATER
POSSIBLE CAUSES
1/2 O2 SENSOR VOLTAGE BTWN 0.4 V & 0.6 V
1/1 O2 SENSOR DEFECTIVE
1/2 O2 SENSOR DEFECTIVE
ASD RELAY OUTPUT CIRCUIT OPEN (1/1 O2 SEN)
ASD RELAY OUTPUT CIRCUIT OPEN (1/2 O2 SEN)
HEATER GROUND CIRCUIT OPEN (1/1 O2 SEN)
HEATER GROUND CIRCUIT OPEN (1/2 O2 SEN)
TEST ACTION APPLICABILITY
1 Ignition On, Engine Not Running
With the DRB, actuate the ASD O2 Sensor Heater test.
Wait two minutes for O2 Sensor voltage to stabilize.
Read the Upstream O2 Sensor voltage.
Is the voltage of the Upstream O2 Sensor between 0.4 and 0.6 volts?All
Ye s®Go To 2
No®Go To 5
2Note: The O2 Sensor voltage staying between 0.4 V and 0.6 V indicates a
problem with that Sensor Circuit.
Ignition Off
Disconnect the Upstream O2 Sensor Connector.
Note: Check connectors - Clean/repair as necessary.
Turn key on.
With the DRB, actuate the O2 Sensor Heater test.
Using a Voltmeter, measure the ASD Relay Output Circuit at Sensor Connector.
Is the voltage above 10.0 volts?All
Ye s®Go To 3
No®Repair the open ASD Relay Output Circuit from O2 sensor
connector back to splice.
Perform Powertrain Verification Test VER-2A.
3 Ignition Off
Disconnect the Upstream O2 Sensor Connector.
Note: Check connectors - Clean/repair as necessary.
Using an Ohmmeter, measure the resistance between the Heater Ground Circuit and
a good ground.
Is the resistance below 5.0 ohms?All
Ye s®Go To 4
No®Repair the open Heater Ground Circuit to the Upstream O2
Sensor.
Perform Powertrain Verification Test VER-2A.
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DRIVEABILITY
ProCarManuals.com
TEST ACTION APPLICABILITY
4 If there are no potential causes remaining, the Upstream O2 Sensor is assumed to be
defective.
View repair options.All
Repair
Replace the Upstream O2 Sensor.
Perform Powertrain Verification Test VER-2A.
5 Ignition Off
Turn key on.
With the DRB, actuate the O2 Sensor Heater test.
Wait two minutes for O2 Sensor voltage to stabilize.
With the DRB, read the Downstream O2 Sensor voltage.
Is the voltage of the Downstream O2 Sensor between 0.4 and 0.6 volts?All
Ye s®Go To 6
No®Test complete.
6Note: The O2 Sensor voltage staying between 0.4 and 0.6 V indicates a
problem with that Sensor Circuit.
Ignition Off
Disconnect the Downstream O2 Sensor Connector.
Note: Check connectors - Clean/repair as necessary.
Turn key on.
With the DRB, actuate the O2 Sensor Heater test.
Using a Voltmeter, measure the ASD Relay Output Circuit in Sensor Connector.
Is the voltage above 10.0 volts?All
Ye s®Go To 7
No®Repair the open ASD Relay Output Circuit from O2 Sensor
Connector back to splice.
Perform Powertrain Verification Test VER-2A.
7 Ignition Off
Disconnect the Downstream O2 Sensor Connector.
Note: Check connectors - Clean/repair as necessary.
Using an Ohmmeter, measure the resistance between the Heater Ground Circuit and
a good ground.
Is the resistance below 5.0 ohms?All
Ye s®Go To 8
No®Repair the open Heater Ground Circuit to the Downstream O2
Sensor.
Perform Powertrain Verification Test VER-2A.
8 If there are no potential causes remaining, the Downstream O2 Sensor is assumed to
be defective.
View repair options.All
Repair
Replace the Downstream O2 Sensor.
Perform Powertrain Verification Test VER-2A.
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DRIVEABILITY
* CHECKING OXYGEN SENSOR HEATER ÐContinued
ProCarManuals.com