Engine Control System - 4.2L - DTC P0140 to P0506: Overview

Test Description

The numbers below refer to the step numbers on the diagnostic table.

2: An HO2S heater fault may set this DTC.
3: If the voltage is varying above and below the specified value, the condition is not present.

Step	Action	Value(s)	Yes	No
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views or Powertrain Control Module (PCM) Connector End Views
1	Did you perform the Diagnostic System Check - Vehicle?		Go to Step 2	Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2	Start the engine. Command the heated oxygen sensor (HO2S) 2 heater ON with a scan tool. Wait 15 seconds to allow the HO2S 2 heater current to stabilize. Observe the HO2S 2 Heater Current parameter with a scan tool. Is the HO2S 2 Heater Current parameter within the specified range?	0.217-1.56 A	Go to Step 3	Go to DTC P0135 or P0141
3	Allow the engine to reach operating temperature. Refer to Scan Tool Data List . Operate the engine at 2,000 RPM for 30 seconds. Quickly cycle the throttle from closed throttle to wide open throttle 3 times while observing the HO2S 2 Voltage parameter with a scan tool. Did the HO2S 2 Voltage parameter change more than the specified value?	200 mV	Go to Step 4	Go to Step 5
4	Observe the Freeze Frame/Failure Records for this DTC. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition?		Go to Step 5	Go to Intermittent Conditions
5	Turn OFF the ignition. Disconnect the HO2S 2. Turn ON the ignition, with the engine OFF. Observe the HO2S 2 Voltage parameter with a scan tool. Is the HO2S 2 Voltage parameter more than the specified value?	800 mV	Go to Step 6	Go to Step 7
6	IMPORTANT: The normal voltage on the high signal circuit is between 400-500 mV. IMPORTANT: The sensor may be damaged if the circuit is shorted to a voltage source. Test the HO2S 2 high signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.Did you find and correct the condition?		Go to Step 18	Go to Step 17
7	Connect a 3-amp fused jumper wire between the high signal circuit of the HO2S 2 harness connector on the engine harness side and the low signal circuit of the HO2S 2 harness connector on the engine harness side. Observe the HO2S 2 Voltage parameter with a scan tool. Is the HO2S 2 Voltage parameter within the specified range?	400-500 mV	Go to Step 9	Go to Step 8
8	Remove the jumper wire from the previous step. Test the HO2S 2 heater low control circuit for a short to one of the following circuits: The HO2S 2 low signal circuit The HO2S 2 high signal circuit Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 18	Go to Step 14
9	Remove the jumper wire from the previous step. Connect a 3-amp fused jumper wire from the high signal circuit of the HO2S 2 harness connector on the engine harness side and ground. Observe the HO2S 2 Voltage parameter with a scan tool. Is the HO2S 2 Voltage parameter within the specified range?	400-500 mV	Go to Step 11	Go to Step 10
10	Remove the jumper wire from the previous step. Test the HO2S 2 low signal circuit for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 18	Go to Step 15
11	Remove the jumper from the previous step. Measure the voltage from the high signal circuit of the HO2S 2 harness connector on the engine harness side to a good ground with a DMM. Refer to Circuit Testing in Wiring Systems. Is the voltage more than the specified value?	1.0 V	Go to Step 12	Go to Step 13
12	IMPORTANT: The normal voltage on the low signal circuit is between 20-100 mV. Test the HO2S 2 low signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.Did you find and correct the condition?		Go to Step 18	Go to Step 17
13	Test the HO2S 2 high signal circuit for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 18	Go to Step 15
14	Test for an intermittent and for a poor connection at the HO2S 2. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 18	Go to Step 16
15	Test for an intermittent and for a poor connection at the powertrain control module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 18	Go to Step 17
16	NOTE: Refer to Heated Oxygen Sensor (HO2S) Resistance Learn Reset Notice in Cautions and Notices. Replace the HO2S 2. Refer to Heated Oxygen Sensor Replacement - Position 2 .Did you complete the replacement?		Go to Step 18
17	Replace the PCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement?		Go to Step 18
18	Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition?		Go to Step 2	Go to Step 19
19	Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed?		Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information	System OK

IMPORTANT
The normal voltage on the high signal circuit is between 400-500 mV.

IMPORTANT
The sensor may be damaged if the circuit is shorted to a voltage source.

IMPORTANT
The normal voltage on the low signal circuit is between 20-100 mV.

NOTE
Refer to Heated Oxygen Sensor (HO2S) Resistance Learn Reset Notice in Cautions and Notices.

DTC P0140

The number below refers to the step number on the diagnostic table.

8: If conditions were not corrected, a worn cam, worn intake or exhaust valves, or other engine mechanical failures may be at fault.

Step	Action	Values	Yes	No
1	Did you perform the Diagnostic System Check - Vehicle?		Go to Step 2	Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2	Are any DTCs other than P0171 also set?		Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information	Go to Step 3
3	Install a scan tool. Review the Freeze Frame/Failure Records and record the displayed data for this DTC. Select the Fuel and Emission data list. Start the engine. Observe the Long Term FT parameter with a scan tool. Is the Long Term FT parameter more than the specified value?	20%	Go to Step 4	Go to Diagnostic Aids
4	Operate the engine at idle. Observe the heated oxygen sensor (HO2S) parameters with a scan tool. Does the scan tool indicate that the HO2S parameters are within the specified range and fluctuating?	200-800 mV	Go to Step 5	Go to Step 6
5	Turn OFF the engine. Visually and physically inspect the following items: Splits, kinks, or improper connections at the vacuum hoses-Refer to Emission Hose Routing Diagram . Low fuel pressure-Refer to Fuel System Diagnosis . Properly functioning fuel injectors-Refer to Fuel Injector Coil Test Fuel contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (with Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (without Special Tool) . Did you find and correct the condition?		Go to Step 9	Go to Step 8
6	Turn OFF the engine. Turn ON the ignition, with the engine OFF. Observe the manifold absolute pressure (MAP) sensor pressure parameter with a scan tool. The MAP sensor pressure should be within the range specified for your altitude. Refer to Altitude vs Barometric Pressure . Do the MAP parameters indicate the correct barometric pressure?		Go to Step 7	Go to DTC P0106
7	Turn OFF the engine. Inspect for the following conditions: Proper HO2S installation Electrical connectors and wires are secured and not contacting the exhaust system An open or a short to ground in the HO2S signal circuit Did you find and correct the condition?		Go to Step 9	Go to Fuel System Diagnosis
8	Operate the engine at idle. Inspect for the following conditions: AIR shut-off valve stuck open Missing, loose, or leaking exhaust components Vacuum leaks at the intake manifold, throttle body, and injector O-rings Leaks at the air intake ducts Leaking crankcase ventilation system Did you find and correct the condition?		Go to Step 9	Go to Symptoms - Engine Mechanical in Engine Mechanical
9	IMPORTANT: After repairs, use the scan tool Fuel Trim Reset function in order to reset the Long Term Fuel Trim. Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition?		Go to Step 2	Go to Step 10
10	Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed?		Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information	System OK

IMPORTANT
After repairs, use the scan tool Fuel Trim Reset function in order to reset the Long Term Fuel Trim.

DTC P0171

System Description

The powertrain control module (PCM) uses information from the crankshaft position (CKP) sensor and the camshaft position (CMP) sensor in order to determine when an engine misfire is occurring. By monitoring variations in the crankshaft rotation speed for each cylinder, the PCM is able to detect individual misfire events. A misfire rate that is high enough can cause the 3-way catalytic converter (TWC) to overheat under certain driving conditions. The malfunction indicator lamp (MIL) will flash ON and OFF when the conditions for TWC overheating are present. If the PCM detects a misfire rate sufficient to cause emission levels to exceed mandated standards, DTC P0300 will set.

The number below refers to the step number on the diagnostic table.

2: If the actual CKP variation values are not within the learned values, the misfire counters may increment.

Step	Action	Values	Yes	No
1	Did you perform the Diagnostic System Check - Vehicle?		Go to Step 2	Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2	Start the engine. Allow the engine to idle or operate within the conditions listed in the Freeze Frame/Failure Records. Monitor all of the Misfire counters with the scan tool. Are any of the Misfire current counters incrementing?		Go to Step 3	Go to Diagnostic Aids
3	Are any other DTCs set?		Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information	Go to Step 4
4	Can any abnormal engine noise be heard?		Go to Symptoms - Engine Mechanical	Go to Step 5
5	Inspect the following components: The vacuum hoses and seals for splits, restrictions, and improper connections-Refer to Engine Controls Schematics . The throttle body and intake manifold for vacuum leaks The crankcase ventilation system for vacuum leaks-Refer to Crankcase Ventilation System Inspection/Description in Engine Mechanical. The powertrain control module (PCM) grounds for corrosion and loose connections-Refer to Ground Distribution Schematics in Wiring Systems. The exhaust system for restrictions-Refer to Restricted Exhaust in Engine Exhaust. The fuel for contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (with Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (without Special Tool) . Did you find and correct the condition?		Go to Step 13	Go to Step 6
6	Remove the spark plugs from the cylinders that indicated a misfire. Refer to Spark Plug Replacement . Inspect the spark plug. Refer to Spark Plug Inspection . Do the spark plugs appear to be OK?		Go to Step 10	Go to Step 7
7	Are the sparks plug oil or coolant fouled?		Go to Symptoms - Engine Mechanical	Go to Step 8
8	Are the spark plugs gas fouled?		Go to Step 11	Go to Step 9
9	Did the spark plugs show any signs of being cracked, worn, or improperly gapped?		Go to Step 12	Go to Step 10
10	Perform the fuel injector coil test. Refer to Fuel Injector Coil Test . Did you find and correct the condition?		Go to Step 13	Go to Symptoms - Engine Mechanical
11	Perform the fuel system diagnosis. Refer to Fuel System Diagnosis . Did you find and correct the condition?		Go to Step 13	Go to Symptoms - Engine Mechanical
12	Replace or gap the spark plugs. Refer to Spark Plug Replacement . Did you complete the action?		Go to Step 13
13	Was the customer concern the malfunction indicator lamp (MIL) flashing?		Go to Step 14	Go to Step 15
14	Operate the vehicle at the specified value for 4 minutes. Operate the vehicle within the Conditions for Running the DTC P0420, as specified in the supporting text. Refer to DTC P0420 . Does DTC P0420 run and pass?	2,500 RPM	Go to Step 15	Go to DTC P0420
15	Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition?		Go to Step 2	Go to Step 16
16	Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed?		Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information	System OK

DTC P0300

The number below refers to the step number on the diagnostic table.

2: If the actual CKP variation values are not within the learned values, the misfire counters may increment.

Step	Action	Values	Yes	No
1	Did you perform the Diagnostic System Check - Vehicle?		Go to Step 2	Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2	Start the engine. Allow the engine to idle or operate within the conditions listed in the Freeze Frame/Failure Records. Monitor all of the Misfire counters with the scan tool. Are any of the Misfire current counters incrementing?		Go to Step 3	Go to Intermittent Conditions
3	Are any other DTCs set?		Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information	Go to Step 4
4	Can any abnormal engine noise be heard?		Go to Symptoms - Engine Mechanical in Engine Mechanical - 4.2L	Go to Step 5
5	Turn OFF the ignition. Remove the fuel pump relay. Refer to Relay Replacement (Within an Electrical Center) or Relay Replacement (Attached to Wire Harness) in Wiring Systems. Remove the ignition coil for the affected cylinder, keeping the ignition connected to the harness connector. Refer to Ignition Coil(s) Replacement . IMPORTANT: Not grounding the ignition coil may cause an erratic spark. Connect a jumper wire between the ignition coil and a good ground. Install the J 26792 Spark Tester on the ignition coil and a good ground. See Special Tools . Crank the engine. Does the spark tester spark?		Go to Step 7	Go to Step 6
6	Inspect the affected cylinder spark plug boot for a missing or damaged ignition coil spring. Did you find and correct the condition?		Go to Step 15	Go to Electronic Ignition (EI) System Diagnosis
7	Remove the spark plug from the cylinder that indicated a misfire. Refer to Spark Plug Replacement . Inspect the spark plug. Refer to Spark Plug Inspection . Does the spark plug appear to be OK?		Go to Step 8	Go to Step 9
8	Exchange the suspected spark plug with another cylinder that is operating properly. Refer to Spark Plug Replacement . Operate the vehicle under the same conditions that the misfire occurred. Did the misfire move with the spark plug?		Go to Step 14	Go to Step 12
9	Is the spark plug oil or coolant fouled?		Go to Symptoms - Engine Mechanical in Engine Mechanical- 4.2L	Go to Step 10
10	Is the spark plug gas fouled?		Go to Step 12	Go to Step 11
11	Did the spark plug show any signs of being cracked, worn, or improperly gapped?		Go to Step 13	Go to Step 12
12	Perform the fuel injector coil test. Refer to Fuel Injector Coil Test . Did you find and correct the condition?		Go to Step 15	Go to Symptoms - Engine Mechanical in Engine Mechanical- 4.2L
13	Replace or gap the spark plug. Refer to Spark Plug Replacement . Did you complete the action?		Go to Step 15
14	Replace the faulty spark plug. Refer to Spark Plug Replacement . Did you complete the replacement?		Go to Step 15
15	Was the customer concern the malfunction indicator lamp (MIL) flashing?		Go to Step 16	Go to Step 17
16	Operate the vehicle at the specified value for 4 minutes. Operate the vehicle within the Conditions for Running the DTC P0420, as specified in the supporting text. Refer to DTC P0420 . Does the DTC run and pass?	2,500 RPM	Go to Step 17	Go to DTC P0420
17	Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition?		Go to Step 2	Go to Step 18
18	Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed?		Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information	System OK

IMPORTANT
Not grounding the ignition coil may cause an erratic spark.

DTC P0301-P0306

The numbers below refer to the step numbers on the diagnostic table.

2: This step ensures that the malfunction is present.
3: This step tests for a KS that is shorted to ground
4: This step tests the KS for proper operation.
5: This step tests for a short to voltage on the KS signal circuit and the KS low reference circuit.

Step	Action	Values	Yes	No
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module (PCM) Connector End Views or Engine Controls Connector End Views
1	Did you perform the Diagnostic System Check - Vehicle?		Go to Step 2	Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2	IMPORTANT: If an engine mechanical noise can be heard, repair the condition before proceeding with this diagnostic. Refer to Symptoms - Engine Mechanical in Engine Mechanical - 4.2L. Observe the Freeze Frame/Failure Records data for this DTC. Turn the ignition OFF for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Does the DTC fail this ignition?		Go to Step 3	Go to Diagnostic Aids
3	Turn OFF the ignition. Disconnect the affected knock sensor (KS). Set the DMM to the ohm scale. Measure the resistance from the signal terminal on the KS to a good ground with the DMM. Measure the resistance from the low reference terminal on the KS to a good ground with the DMM. Does the DMM display OL for both terminals?		Go to Step 4	Go to Step 10
4	Connect the DMM between the terminals of the affected KS. Set the DMM to the 400 mV AC hertz scale and wait for the DMM to stabilize at 0 Hz. Refer to Measuring Frequency in Wiring Systems. IMPORTANT: Do not tap on plastic engine components. Tap on the engine block with a non-metallic object near the affected KS while observing the signal indicated on the DMM. Does the DMM display a fluctuating frequency while tapping on the engine block?		Go to Step 5	Go to Step 10
5	Turn ON the ignition, with the engine OFF. Measure the voltage at the KS signal circuit to a good ground with a DMM. Measure the voltage at the KS low reference circuit to a good ground with a DMM. Does the DMM display a voltage above the specified value on either circuit?	1 V	Go to Step 6	Go to Step 7
6	Turn OFF the ignition. Disconnect the powertrain control module (PCM). Test the KS signal circuit or the KS low reference circuit for a short to voltage. Refer to Testing for a Short to Voltage and Wiring Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 12	Go to Step 11
7	Turn OFF the ignition. Disconnect the PCM. Test the KS signal circuit and the KS low reference circuit for an open, for a high resistance, and for a short to ground. Refer to Testing for Continuity , Testing for Short to Ground and Wiring Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 12	Go to Step 9
8	Test for an intermittent and for a poor connection at the affected KS. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 12	Go to Step 10
9	Test for an intermittent and for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 12	Go to Step 11
10	Replace the affected KS. Refer to Knock Sensor (KS) Replacement . Did you complete the replacement?		Go to Step 12
11	Replace the PCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement?		Go to Step 12
12	Clear the DTCs with a scan tool. Turn the ignition OFF for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Does the DTC fail this ignition?		Go to Step 2	Go to Step 13
13	Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed?		Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information	System OK

IMPORTANT
If an engine mechanical noise can be heard, repair the condition before proceeding with this diagnostic. Refer to Symptoms - Engine Mechanical in Engine Mechanical - 4.2L.

IMPORTANT
Do not tap on plastic engine components.

DTC P0327 or P0332

The number below refers to the step number on the diagnostic table.

6: This step tests the output of the CMP sensor. If the duty cycle is not within the specified range the sensor is bad.

Step	Action	Values	Yes	No
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module (PCM) Connector End Views or Engine Controls Connector End Views
1	Did you perform the Diagnostic System Check - Vehicle?		Go to Step 2	Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2	Start the engine. Observe the Camshaft Position (CMP) Active Counter parameter with a scan tool. Does the scan tool parameter increment?		Go to Step 3	Go to Step 4
3	Observe the Freeze Frame/Failure Records for this DTC. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition?		Go to Step 4	Go to Diagnostic Aids
4	Turn OFF the ignition. Disconnect the CMP sensor. Turn ON the ignition, with the engine OFF. Measure the voltage from the 12-volt reference circuit to a good ground with a DMM. Refer to Probing Electrical Connectors in Wiring Systems. Is the voltage more than the specified value?	10 V	Go to Step 5	Go to Step 7
5	Turn OFF the ignition. Jumper the CMP circuits from the CMP sensor to the CMP sensor harness connector. Refer to Using Connector Test Adapters in Wiring Systems. Turn ON the ignition, with the engine OFF. Measure the Voltage Drop from the low reference circuit of the CMP sensor to a good ground with a DMM. Refer to Circuit Testing in Wiring Systems. Is the voltage more than the specified value?	0.2 V	Go to Step 8	Go to Step 6
6	Leave the jumper wires installed. Remove the jumper wire from the CMP signal circuit on the powertrain control module (PCM) side. Start the engine. Measure the duty cycle from the CMP signal circuit on the sensor side and to a good ground with a DMM. Is the duty cycle within the specified range?	40-50%	Go to Step 9	Go to Step 10
7	Test the 12-volt reference circuit for an open, high resistance or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 15	Go to Step 11
8	Test the low reference circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 15	Go to Step 11
9	Test the signal circuit for an open, short to ground or a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 15	Go to Step 11
10	Test for an intermittent and for a poor connection at the CMP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 15	Go to Step 12
11	Test for an intermittent and for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 15	Go to Step 14
12	Remove the CMP sensor. Visually inspect the CMP sensor for the following conditions: Physical damage Loose or improper installation Did you find and correct the condition?		Go to Step 15	Go to Step 13
13	Replace the CMP sensor. Refer to Camshaft Position (CMP) Sensor Replacement . Did you complete the replacement?		Go to Step 15
14	Replace the PCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement?		Go to Step 15
15	Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition?		Go to Step 2	Go to Step 16
16	Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed?		Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information	System OK

DTC P0340

The number below refers to the step number on the diagnostic table.

4: The counter should stop incrementing with the sensor electrical connector disconnected and set a DTC P0340. If the counter stills increments, this indicates that the PCM is malfunctioning.

Step	Action	Value(s)	Yes	No
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module (PCM) Connector End Views or Engine Controls Connector End Views
1	Did you perform the Diagnostic System Check - Vehicle?		Go to Step 2	Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2	Turn ON the ignition, with the engine OFF. Are any other DTCs set?		Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information	Go to Step 3
3	Start the engine. Observe the camshaft position (CMP) Resync Counter on the scan tool. Is the CMP Resync Counter incrementing?		Go to Step 4	Go to Diagnostic Aids
4	Turn OFF the ignition. Disconnect the CMP sensor. Start the engine. Observe the CMP Resync on the scan tool. Did the CMP Resync Counter stop incrementing?		Go to Step 5	Go to Step 6
5	Turn OFF the engine. With the CMP connector still disconnected, connect a DMM set to the DC HZ scale from the CMP signal circuit, powertrain control module (PCM) side, to ground. Start the engine. Does the DMM display a Hertz reading above the specified value?	0 Hz	Go to Step 6	Go to Step 7
6	Visually and physically inspect all circuits going to the CMP sensor for the following: Being routed too close to secondary ignition wires or components Being routed too close to after-market add-on electrical equipment Being routed too close to solenoids, relays, and motors If you find incorrect routing, correct the harness routing. Did you find and correct the condition?		Go to Step 11	Go to Step 9
7	Test for an intermittent and for a poor connection at the CMP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 11	Go to Step 8
8	Replace the CMP sensor. Refer to Camshaft Position (CMP) Sensor Replacement . Did you complete the replacement?		Go to Step 11
9	Disconnect the PCM. Check the CMP terminals for a faulty electrical connection. Repair the terminals as necessary. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 11	Go to Step 10
10	Replace the PCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement?		Go to Step 11
11	Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition?		Go to Step 12	Go to Step 2
12	Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed?		Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information	System OK

DTC P0341

The numbers below refer to the step numbers on the diagnostic table.

9: This step determines if excessive resistance on the supply voltage circuit between the AIR fuse and the AIR pump relay is the cause for an inoperative AIR pump. Two ohms of resistance on this circuit can prevent the AIR pump from running.
13: This step determines if excessive resistance on the AIR pump relay circuit and PCM driver is the cause for an inoperative AIR pump relay. The test lamp in series is intended to generate a electrical load on this circuit. 90 ohms of resistance on this circuit can prevent the AIR pump relay from operating.
17: This step determines if excessive resistance on the supply circuit is the cause for an inoperative AIR pump. Two ohms of resistance on this circuit can prevent the AIR pump from running.
18: This step determines if excessive resistance on the ground circuit is the cause for an inoperative AIR pump. Two ohms of resistance on this circuit can prevent the AIR pump from running.
19: This step determines if the AIR system is operating normally.

Step	Action	Values	Yes	No
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module (PCM) Connector End Views or Engine Controls Connector End Views
1	Did you perform the Diagnostic System Check - Vehicle?		Go to Step 2	Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2	Turn ON the ignition, with the engine OFF. Listen for secondary air injection (AIR) pump operation. Does the AIR pump run continuously?		Go to Step 3	Go to Step 4
3	Remove the AIR pump relay. Refer to Relay Replacement (Within an Electrical Center) or Relay Replacement (Attached to Wire Harness) in Wiring Systems. Does the AIR pump continue to operate?		Go to Step 52	Go to Step 5
4	IMPORTANT: The AIR pump has an internal circuit breaker to protect the pump from overheating. Intermittent AIR pump operation during testing may be normal. Command the AIR pump relay ON and OFF with a scan tool. Listen for AIR pump operation. Does the AIR pump turn ON and OFF when commanded with a scan tool?		Go to Step 19	Go to Step 6
5	Turn OFF the ignition. Probe the control circuit of the AIR pump relay with a test lamp that is connected to battery voltage. Refer to Probing Electrical Connectors in Wiring Systems. Does the test lamp illuminate?		Go to Step 38	Go to Step 54
6	Remove the underhood fuse block cover. Inspect the AIR fuse. Is the fuse open?		Go to Step 34	Go to Step 7
7	Probe both test points of the AIR SOL fuse at the underhood fuse block. Does the test lamp illuminate at both test points?		Go to Step 8	Go to Step 31
8	Turn OFF the ignition. Remove the AIR pump relay located near the AIR pump. Refer to Relay Replacement (Within an Electrical Center) or Relay Replacement (Attached to Wire Harness) in Wiring Systems. Probe the battery positive voltage circuit, switched side, of the AIR pump relay with a test lamp that is connected to a good ground. Refer to Probing Electrical Connectors in Wiring Systems. Does the test lamp illuminate?		Go to Step 9	Go to Step 46
9	Connect a J 36169-HD Heavy Duty Fused Jumper Wire between the battery positive voltage circuit and the AIR pump supply voltage circuit at the AIR relay connector. See Special Tools . Refer to Using Fused Jumper Wires in Wiring Systems. Measure the voltage drop from the battery positive circuit, switched side, of the AIR pump relay at the relay connector to battery voltage. Refer to Circuit Testing and Measuring Voltage Drop in Wiring Systems. Is the voltage drop less than the specified value?	0.6 V	Go to Step 10	Go to Step 46
10	Remove the J 36169-HD . See Special Tools . Turn ON the ignition, with the engine OFF. Probe the ignition 1 voltage circuit, coil side, of the AIR pump relay with a test lamp that is connected to a good ground. Refer to Probing Electrical Connectors in Wiring Systems. Does the test lamp illuminate?		Go to Step 11	Go to Step 48
11	Measure the resistance of the ignition 1 voltage circuit from the AIR relay connector to the AIR SOL fuse. Is the resistance less than the specified value?	10 ohms	Go to Step 12	Go to Step 48
12	Probe the control circuit of the AIR pump relay with a test lamp that is connected to battery voltage. Refer to Probing Electrical Connectors in Wiring Systems. Command the AIR pump relay ON and OFF with a scan tool. Does the test lamp turn ON and OFF when commanded with a scan tool?		Go to Step 13	Go to Step 30
13	Measure the resistance of the AIR pump relay control circuit from the AIR pump relay connector to the powertrain control module (PCM) connector with a DMM. Refer to Circuit Testing in Wiring Systems. Is the resistance less than the specified value?	10 ohms	Go to Step 14	Go to Step 47
14	Connect a J 36169-HD between the battery positive voltage circuit, switched side, and the AIR pump supply voltage circuit at the AIR pump relay connector. See Special Tools . Refer to Using Fused Jumper Wires in Wiring Systems. Listen for AIR pump operation. Does the AIR pump turn ON?		Go to Step 42	Go to Step 15
15	Ensure the J 36169-HD is installed. See Special Tools . Disconnect the AIR pump connector. Probe the AIR pump supply voltage circuit with a test lamp connected to a good ground. Refer to Probing Electrical Connectors in Wiring Systems. Does the test lamp illuminate?		Go to Step 16	Go to Step 49
16	Connect a test lamp between the AIR pump supply voltage circuit and the AIR pump ground circuit at the AIR pump harness connector. Does the test lamp illuminate?		Go to Step 17	Go to Step 50
17	Remove the J 36169-HD from the relay connector. See Special Tools . Connect a J 35616 GM Approved Terminal Test Kit to each of the terminals at the AIR pump harness connector and the corresponding terminal at the AIR pump. Refer to Using Connector Test Adapters in Wiring Systems. Connect the fused jumper wire J 36169-HD at the AIR pump relay connector. See Special Tools . Measure the voltage drop from the AIR pump supply circuit of the AIR pump connector to the AIR pump supply circuit at the AIR pump relay, with a DMM. Refer to Measuring Voltage Drop in Wiring Systems. Is the voltage drop less than the specified value?	0.6 V	Go to Step 18	Go to Step 49
18	Measure the voltage drop from the AIR pump ground circuit of the AIR pump, to a good ground with a DMM. Refer to Measuring Voltage Drop in Wiring Systems. Is the voltage drop less than the specified value?	0.6 V	Go to Step 43	Go to Step 50
19	Start and idle the engine until Closed Loop operation is achieved. Monitor the HO2S 1 Voltage parameter with a scan tool. Command the AIR pump system ON with a scan tool. Does the HO2S 1 Voltage parameter decrease below the specified value?	75 mV	Go to Diagnostic Aids	Go to Step 20
20	Turn OFF the ignition. Disconnect the AIR pump outlet hose from the AIR shut-off valve. Start and idle the engine. Command the AIR pump relay ON with a scan tool. Is a pressurized airflow present at the AIR pump outlet hose?		Go to Step 21	Go to Step 40
21	Turn OFF the ignition. Disconnect the AIR solenoid connector at the AIR shut-off valve. Probe the AIR solenoid ground circuit with a test lamp that is connected to battery voltage. Refer to Probing Electrical Connectors in Wiring Systems. Does the test lamp illuminate?		Go to Step 22	Go to Step 47
22	Turn the ignition to the ON position. Probe the AIR solenoid supply voltage circuit at the solenoid with a test lamp that is connected to a good ground. Refer to Probing Electrical Connectors in Wiring Systems. Command the AIR pump relay ON with a scan tool. Does the test lamp illuminate?		Go to Step 23	Go to Step 25
23	Measure the resistance of the following circuits: The AIR solenoid supply voltage circuit The AIR solenoid ground circuit Is the resistance on each circuit less than the specified amount?	10 ohms	Go to Step 24	Go to Step 47
24	Ensure the AIR pump outlet hose is removed from the AIR shut-off valve. Connect a J 36169-A Fused Jumper Wire from battery positive voltage to either terminal of the AIR solenoid. Start and idle the engine. Momentarily touch the other terminal of the AIR solenoid to a good ground with a jumper wire, 5 times for a duration of 2 seconds each. Is an audible exhaust sound heard at the inlet of the AIR shut-off valve, each time the circuit is connected to a ground?		Go to Intermittent Conditions	Go to Step 57
25	Turn ON the ignition, with the engine OFF. Connect the AIR solenoid. Remove the AIR solenoid relay. Probe both battery positive voltage circuits at the switched side and the coil side of the AIR solenoid relay connector with a test lamp that is connected to a good ground. Refer to Probing Electrical Connectors in Wiring Systems. Does the test lamp illuminate at both circuits?		Go to Step 26	Go to Step 53
26	Probe the control circuit of the AIR solenoid relay at the underhood fuse block with a test lamp connected to battery voltage. Refer to Probing Electrical Connectors in Wiring Systems. Command the AIR system ON and OFF with a scan tool. Does the test lamp turn ON and OFF?		Go to Step 28	Go to Step 27
27	Does the test lamp remain illuminated?		Go to Step 38	Go to Step 30
28	Measure the resistance of the AIR solenoid relay control circuit from the AIR solenoid relay connector to the PCM connector with a DMM. Refer to Circuit Testing in Wiring Systems. Is the resistance less than the specified value?	10 ohms	Go to Step 29	Go to Step 47
29	IMPORTANT: The fuse rating shall not exceed the load rating of the jumper wire. Connect a J 36169-A between the switched side voltage circuit and the AIR solenoid supply voltage circuit at the AIR solenoid relay connector in the underhood fuse block. Disconnect the AIR solenoid connector. Probe the AIR solenoid supply voltage circuit at the solenoid connector. Does the test lamp illuminate?		Go to Step 45	Go to Step 51
30	Test the AIR relay control circuit for an open or short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 59	Go to Step 44
31	Does the test lamp illuminate at one side of the AIR SOL fuse?		Go to Step 32	Go to Step 53
32	Test the AIR solenoid supply voltage circuit for a short to ground. Refer to Wiring Repairs and Circuit Testing in Wiring Systems. Replace the AIR solenoid fuse as necessary. Did you find and correct the condition?		Go to Step 60	Go to Step 33
33	Measure the resistance of the AIR solenoid. Is the resistance within the specified range?	4-8 ohms	Go to Step 39	Go to Step 57
34	Test the battery positive voltage circuit between the AIR fuse and the relay for a short to ground. Refer to Wiring Repairs and Circuit Testing in Wiring Systems. Replace the AIR fuse as necessary. Did you find and correct the condition?		Go to Step 60	Go to Step 35
35	Test the AIR pump supply voltage circuit for a short to voltage. Refer to Wiring Repairs and Circuit Testing in Wiring Systems. Did you find and correct the condition?		Go to Step 59	Go to Step 36
36	Test the AIR pump supply voltage circuit for a short to ground. Refer to Wiring Repairs and Circuit Testing in Wiring Systems. Did you find and correct the condition?		Go to Step 60	Go to Step 37
37	Install the AIR pump relay. Replace the AIR fuse as necessary. Connect the AIR pump, as necessary. Turn ON the ignition, with the engine OFF. Command the AIR pump system ON with a scan tool. Does the AIR pump turn ON with a scan tool?		Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems	Go to Step 56
38	Test the AIR relay control circuit for a short to ground. Refer to Wiring Repairs and Circuit Testing in Wiring Systems. Did you find and correct the condition?		Go to Step 59	Go to Step 44
39	Test all of the ignition 1 voltage circuits supplied by the AIR SOL fuse for a short to ground. Refer to Wiring Repairs and Circuit Testing in Wiring Systems. Replace the AIR SOL fuse as necessary. Did you find and correct the condition?		Go to Step 60	Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems
40	Inspect the AIR pump outlet hose for the following conditions: Restrictions Leaks Did you find and correct the condition?		Go to Step 60	Go to Step 41
41	Inspect for a restriction at the following locations: The AIR pump inlet hose The engine air cleaner housing Did you find and correct the condition?		Go to Step 60	Go to Step 56
42	Test for an intermittent and for a poor connection at the AIR pump relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 59	Go to Step 54
43	Test for an intermittent and for a poor connections at the AIR pump. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 59	Go to Step 56
44	Test for shorted connections or for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 59	Go to Step 58
45	Test for an intermittent and for a poor connection at the AIR solenoid relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 60	Go to Step 55
46	Repair the open or high resistance in the battery positive circuit between the AIR pump fuse and the AIR pump relay. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair?		Go to Step 60
47	Repair the circuit with the open or high resistance. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair?		Go to Step 60
48	Repair the open or high resistance in the ignition 1 voltage circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair?		Go to Step 60
49	Repair the open or high resistance in the AIR pump supply voltage circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair?		Go to Step 60
50	Repair the open or high resistance in the AIR pump ground circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair?		Go to Step 60
51	Repair the open or high resistance in the AIR solenoid supply voltage circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair?		Go to Step 60
52	Repair the short to voltage in the AIR pump supply voltage circuit. Refer to Wiring Repairs in Wiring Systems. Replace the AIR solenoid fuse as necessary. Did you complete the repair?		Go to Step 59
53	Replace the underhood fuse block. Refer to Underhood Electrical Center or Junction Block Replacement in Wiring Systems. Did you complete the replacement?		Go to Step 60
54	Replace the AIR pump relay. Refer to Relay Replacement (Within an Electrical Center) or Relay Replacement (Attached to Wire Harness) in Wiring Systems. Did you complete the replacement?		Go to Step 59
55	Replace the AIR solenoid relay. Refer to Relay Replacement (Within an Electrical Center) or Relay Replacement (Attached to Wire Harness) in Wiring Systems. Did you complete the replacement?		Go to Step 60
56	Replace the AIR pump. Refer to Secondary Air Injection (AIR) Pump Replacement . Did you complete the replacement?		Go to Step 59
57	Replace the AIR electronic shut-off valve assembly. Refer to Secondary Air Injection (AIR) Solenoid Valve Replacement . Did you complete the replacement?		Go to Step 60
58	Replace the PCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement?		Go to Step 59
59	Ensure all components and connectors are installed and secured. Replace fuses, as necessary. Turn the ignition ON, with the engine OFF. Command the AIR pump relay ON and OFF. Listen for AIR pump operation. Does the AIR pump turn ON and OFF when commanded with a scan tool?		Go to Step 60	Go to Step 2
60	Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition?		Go to Step 2	Go to Step 61
61	Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed?		Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information	System OK

IMPORTANT
The AIR pump has an internal circuit breaker to protect the pump from overheating. Intermittent AIR pump operation during testing may be normal.

IMPORTANT
The fuse rating shall not exceed the load rating of the jumper wire.

DTC P0410

This DTC tests the evaporative emission (EVAP) system for a small leak. The control module monitors the fuel tank pressure (FTP) sensor signal to determine the vacuum decay rate. At an appropriate time, the control module turns the EVAP canister purge solenoid valve ON and the EVAP canister vent solenoid valve ON. This allows the engine to draw a vacuum on the EVAP system. At a calibrated time, or vacuum level, the control module turns the EVAP canister purge solenoid valve OFF, sealing the system, and monitors the FTP sensor input in order to determine the EVAP system vacuum decay. If the control module detects a leak larger than a calibrated amount, this DTC sets.

The following table illustrates the relationship between the ON and OFF states, and the Open or Closed states of the EVAP canister purge and vent solenoid valves.

Control Module Command	EVAP Canister Purge Solenoid Valve	EVAP Canister Vent Solenoid Valve
ON	Open	Closed
OFF	Closed	Open

DTC P0442

The numbers below refer to the step numbers on the diagnostic table.

3: Introducing smoke in 15 second intervals may allow smaller leak areas to be more noticeable. When the system is less pressurized, the smoke will sometimes escape in a more condensed manner.
5: This step verifies that repairs are complete and that no other condition is present.

Step	Action	Yes	No
Schematic Reference: Evaporative Emissions (EVAP) Hose Routing Diagram Connector End View Reference: Powertrain Control Module (PCM) Connector End Views or Engine Controls Connector End Views
1	Did you perform the Diagnostic System Check - Vehicle?	Go to Step 2	Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2	Inspect the evaporative emission (EVAP) system for the following conditions: A loose, missing, or damaged service port dust cap and/or Schrader valve A loose, incorrect, missing, or damaged fuel fill cap A damaged EVAP canister purge solenoid valve Raise the vehicle on a hoist. Refer to Lifting and Jacking the Vehicle in General Information. Inspect the EVAP system for the following conditions: Any disconnected, improperly routed, kinked, or damaged EVAP pipes and hose A damaged EVAP canister vent solenoid valve or EVAP canister Did you find and correct the condition?	Go to Step 5	Go to Step 3
3	IMPORTANT: Ensure that the vehicle underbody temperature is similar to the ambient temperature and allow the surrounding air to stabilize before starting the diagnostic procedure. System flow will be less with higher temperatures. Turn OFF the ignition. Connect the J 41413-200 Evaporative Emissions System Tester (EEST) power supply clips to a known good 12-volt source. See Special Tools . Install the J 41415-40 Fuel Tank Cap Adapter to the fuel fill pipe. See Special Tools . Connect the fuel fill cap to the J 41415-40 . See Special Tools . Connect the J 41413-200 nitrogen/smoke supply hose to the J 41415-40 . See Special Tools . Turn ON the ignition with the engine OFF. Command the EVAP vent solenoid closed with a scan tool. Turn the nitrogen/smoke valve on the J 41413-200 control panel to SMOKE. See Special Tools . Use the remote switch to introduce smoke into the EVAP system. Use the J 41413-VLV EVAP Service Port Vent Fitting to open the EVAP service port. See Special Tools . Remove the J 41413-VLV once smoke is observed. See Special Tools . Continue to introduce smoke into the EVAP system for an additional 60 seconds. Inspect the entire EVAP system for exiting smoke with the J 41413-SPT High Intensity White Light. See Special Tools . Continue to introduce smoke at 15 second intervals until the leak source has been located. Did you locate and repair a leak source?	Go to Step 5	Go to Step 4
4	Disconnect the J 41415-40 from the fuel fill pipe. See Special Tools . Install the fuel fill cap to the fuel fill pipe. Connect the J 41413-200 nitrogen/smoke supply hose to the EVAP service port. See Special Tools . Use the remote switch to introduce smoke into the EVAP system. Inspect the entire EVAP system for exiting smoke with the J 41413-SPT . See Special Tools . Continue to introduce smoke at 15 second intervals until the leak source has been located. Did you locate and repair a leak source?	Go to Step 5	Go to Diagnostic Aids
5	IMPORTANT: Larger volume fuel tanks and/or those with lower fuel levels may require several minutes for the floating indicator to stabilize. Turn the nitrogen/smoke valve to nitrogen. Connect the nitrogen/smoke hose to the 0.5 mm (0.20 in) test orifice on the bottom-front of the J 41413-200 . See Special Tools . Use the remote switch to activate the J 41413-200 . See Special Tools . Align the red flag on the flow meter with the floating indicator. Use the remote switch to de-activate the J 41413-200 . See Special Tools . Install the J 41415-40 to the fuel fill pipe. See Special Tools . Remove the nitrogen/smoke hose from the test orifice and install the hose onto the J 41415-40 . See Special Tools . Turn ON the ignition, with the engine OFF. Command the EVAP canister vent solenoid valve closed with a scan tool. Use the remote switch to introduce nitrogen and fill the EVAP system until the floating stabilizes. Compare the flow meter's stable floating indicator position to the red flag. Is the floating indicator below the red flag?	Go to Step 6	Go to Step 2
6	Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed?	Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information	System OK

IMPORTANT
Ensure that the vehicle underbody temperature is similar to the ambient temperature and allow the surrounding air to stabilize before starting the diagnostic procedure. System flow will be less with higher temperatures.

IMPORTANT
Larger volume fuel tanks and/or those with lower fuel levels may require several minutes for the floating indicator to stabilize.

DTC P0442

This DTC tests the evaporative emission (EVAP) system for a restricted or blocked EVAP vent path. The control module commands the EVAP canister purge solenoid valve Open and the EVAP canister vent solenoid valve Closed. This allows vacuum to be applied to the EVAP system. Once a calibrated vacuum level has been reached, the control module commands the EVAP canister purge solenoid valve Closed and the EVAP canister vent solenoid valve Open. The control module monitors the fuel tank pressure (FTP) sensor for a decrease in vacuum. If the vacuum does not decrease to near 0 inches H2O in a calibrated time, this DTC sets.

The following table illustrates the relationship between the ON and OFF states, and the Open or Closed states of the EVAP canister purge and vent solenoid valves.

Control Module Command	EVAP Canister Purge Solenoid Valve	EVAP Canister Vent Solenoid Valve
ON	Open	Closed
OFF	Closed	Open

DTC P0446

The numbers below refer to the step numbers on the diagnostic table.

5: This step inspects the EVAP canister vent solenoid valve electrical operation.
6: This step inspects for a restricted EVAP canister vent solenoid valve.
7: This step tests if the restriction is in the EVAP canister or the vent hose.

Step	Action	Values	Yes	No
Schematic Reference: Evaporative Emissions (EVAP) Hose Routing Diagram and Engine Controls Schematics Connector End View Reference: Powertrain Control Module (PCM) Connector End Views or Engine Controls Connector End Views
1	Did you perform the Diagnostic System Check - Vehicle?		Go to Step 2	Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2	Inspect the evaporative emission (EVAP) system for the following conditions: A damaged EVAP canister vent solenoid valve-Refer to Evaporative Emission (EVAP) Canister Vent Solenoid Valve Replacement . A pinched EVAP vent hose A damaged EVAP canister-Refer to Evaporative Emission (EVAP) Canister Replacement (TrailBlazer, Envoy, Rainier) or Evaporative Emission (EVAP) Canister Replacement (Trailblazer EXT, Envoy XL, Envoy XUV) . Did you find and correct the condition?		Go to Step 17	Go to Step 3
3	Turn OFF the ignition. Disconnect the EVAP purge line from the EVAP canister purge solenoid valve. Refer to Evaporative Emission (EVAP) Canister Purge Solenoid Valve Replacement . Turn ON the ignition, with the engine OFF. Is the Fuel Tank Pressure Sensor parameter within the Specified range?	1 to +1 in H2O	Go to Step 4	Go to Step 10
4	IMPORTANT: DO NOT exceed the specified value in this step. Exceeding the specified value may produce incorrect test results. Turn OFF the ignition. Connect the EVAP purge pipe. Connect the J 41413-200 Evaporative Emissions System Tester (EEST) power supply clips to a known good 12-volt source. See Special Tools . Install the J 41415-40 Fuel Fill Cap Adapter to the fuel fill pipe. See Special Tools . Connect the fuel fill cap to the J 41415-40 . See Special Tools . Connect the J 41413-200 nitrogen/smoke supply hose to the J 41415-40 . See Special Tools . Turn ON the ignition, with the engine OFF. Command the EVAP canister vent solenoid valve closed with a scan tool. Turn the nitrogen/smoke valve on the J 41413-200 control panel to NITROGEN. See Special Tools . Use the remote switch to pressurize the EVAP system to the first specified value. Observe the FTP Sensor parameter with a scan tool. Command the EVAP canister vent solenoid valve open with a scan tool. Is the Fuel Tank Pressure Sensor parameter less than the second specified value?	5 in H2O 1 in H2O	Go to Diagnostic Aids	Go to Step 5
5	Command the EVAP canister vent solenoid valve ON and OFF with a scan tool. Do you hear or feel the EVAP canister vent solenoid valve click when commanded ON and OFF?		Go to Step 6	Go to Step 8
6	Disconnect the EVAP vent hose from the EVAP canister vent solenoid valve. Is the Fuel Tank Pressure Sensor parameter less than the specified value?	1 in H2O	Go to Step 12	Go to Step 7
7	Disconnect the EVAP vent hose from the EVAP canister. Is the Fuel Tank Pressure Sensor parameter less than the specified value?	1 in H2O	Go to Step 14	Go to Step 13
8	Disconnect the EVAP canister vent solenoid valve. Probe the control circuit of the EVAP canister vent solenoid valve with a test lamp that is connected to battery voltage. Refer to Probing Electrical Connectors in Wiring Systems. Does the test lamp illuminate?		Go to Step 9	Go to Step 12
9	Test the control circuit of the EVAP canister vent solenoid valve for a short to ground. Refer to Testing for Short to Ground and Wiring Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 17	Go to Step 11
10	Test for an intermittent and for a poor connection at the fuel tank pressure (FTP) sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 17	Go to Step 15
11	Test for an intermittent and for a poor connection at the control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 17	Go to Step 16
12	Replace the EVAP canister vent solenoid valve. Refer to Evaporative Emission (EVAP) Canister Vent Solenoid Valve Replacement . Did you complete the replacement?		Go to Step 17
13	Replace the EVAP canister. Refer to Evaporative Emission (EVAP) Canister Replacement (TrailBlazer, Envoy, Rainier) or Evaporative Emission (EVAP) Canister Replacement (Trailblazer EXT, Envoy XL, Envoy XUV) . Did you complete the replacement?		Go to Step 17
14	Repair the pinched or restricted EVAP vent hose. Did you complete the repair?		Go to Step 17
15	Replace the FTP sensor. Refer to Fuel Tank Pressure Sensor Replacement . Did you complete the replacement?		Go to Step 17
16	Replace the powertrain control module (PCM). Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement?		Go to Step 17
17	IMPORTANT: Do not exceed the specified value in this step. Exceeding the specified value may produce incorrect test results. Turn OFF the ignition. Connect all disconnected components. Connect the J 41413-200 to the fuel fill pipe. See Special Tools . Turn ON the ignition, with the engine OFF. Command the EVAP canister vent solenoid valve closed with a scan tool. Turn the nitrogen/smoke valve on the J 41413-200 control panel to NITROGEN. See Special Tools . Use the remote switch to pressurize the EVAP system to the first specified value. Observe the Fuel Tank Pressure Sensor parameter with a scan tool. Command the EVAP canister vent solenoid valve open with a scan tool. Is the Fuel Tank Pressure Sensor parameter less than the second specified value?	5 in H2O 1 in H2O	Go to Step 18	Go to Step 2
18	Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed?		Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information	System OK

IMPORTANT
DO NOT exceed the specified value in this step. Exceeding the specified value may produce incorrect test results.

IMPORTANT
Do not exceed the specified value in this step. Exceeding the specified value may produce incorrect test results.

DTC P0446

The numbers below refer to the step numbers on the diagnostic table.

2: This step verifies that the condition is present.
4: This step tests the 5-volt reference of the FTP sensor.
5: This step tests if another component is causing the 5-volt reference circuit condition.
6: If the scan tool displays 5 volts, the FTP sensor signal circuit, the FTP sensor 5-volt reference circuit, and the control module are OK.

Step	Action	Values	Yes	No
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module (PCM) Connector End Views or Engine Controls Connector End Views
1	Did you perform the Diagnostic System Check - Vehicle?		Go to Step 2	Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2	Observe the Fuel Tank Pressure Sensor parameter with a scan tool. Is the Fuel Tank Pressure Sensor parameter less than the specified value?	0.1 V	Go to Step 4	Go to Step 3
3	Observe the Freeze Frame/Failure Records for this DTC. Turn OFF the ignition for 30 seconds. Turn ON the ignition, with the engine OFF. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition?		Go to Step 4	Go to Intermittent Conditions
4	Turn ON the ignition, with the engine OFF. Disconnect the fuel tank pressure (FTP) sensor. Measure the voltage from the 5-volt reference circuit of the FTP sensor to a good ground with a DMM. Refer to Circuit Testing in Wiring Systems. Is the voltage within the specified value?	4.8-5.2 V	Go to Step 6	Go to Step 5
5	Disconnect the following components, while monitoring the DMM: The manifold absolute pressure (MAP) sensor The throttle position (TP) sensor The A/C pressure sensor Is the DMM within the specified value when any of the components are disconnected?	4.8-5.2 V	Go to Step 11	Go to Step 7
6	Connect a 3-amp fused jumper wire between the 5-volt reference circuit of the FTP sensor and the signal circuit of the FTP sensor. Observe the Fuel Tank Pressure Sensor parameter with a scan tool. Is Fuel Tank Pressure Sensor parameter within the specified value?	4.8-5.2 V	Go to Step 9	Go to Step 8
7	Test the FTP 5-volt reference circuit for an open or for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 14	Go to Step 10
8	Test the FTP signal circuit for an open or for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 14	Go to Step 10
9	Test for an intermittent and for a poor connection at the FTP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 14	Go to Step 12
10	Test for an intermittent and for a poor connection at the control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 14	Go to Step 13
11	Replace the component that affected the 5-volt reference circuit. Refer to Throttle Body Assembly Replacement , Manifold Absolute Pressure (MAP) Sensor Replacement , or Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement in Heating, Ventilation and Air Conditioning. Did you complete the replacement?		Go to Step 14
12	Replace the FTP sensor. Refer to Fuel Tank Pressure Sensor Replacement . Did you complete the replacement?		Go to Step 14
13	Replace the powertrain control module (PCM). Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement?		Go to Step 14
14	Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition?		Go to Step 2	Go to Step 15
15	Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed?		Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information	System OK

DTC P0452

The numbers below refer to the step numbers on the diagnostic table.

2: This step determines if the condition is present.

4: This step tests the signal circuit of the FTP sensor.
6: This step tests the 5-volt reference circuit of the FTP sensor.

Step	Action	Values	Yes	No
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module (PCM) Connector End Views or Engine Controls Connector End Views
1	Did you perform the Diagnostic System Check - Vehicle?		Go to Step 2	Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2	Turn OFF the ignition. Remove the fuel cap. Turn ON the ignition, with the engine OFF. Observe the Fuel Tank Pressure Sensor parameter with a scan tool. Is the Fuel Tank Pressure Sensor parameter more than the specified value?	4.3 V	Go to Step 4	Go to Step 3
3	Observe the Freeze Frame/Failure Records for this DTC. Turn OFF the ignition for 30 seconds. Turn ON the ignition, with the engine OFF. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition?		Go to Step 4	Go to Intermittent Conditions
4	Install the fuel cap. Disconnect the fuel tank pressure (FTP) sensor. Observe the Fuel Tank Pressure Sensor parameter with a scan tool. Is the Fuel Tank Pressure Sensor parameter more than the specified value?	0.2 V	Go to Step 5	Go to Step 7
5	Test the FTP low reference circuit for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 13	Go to Step 6
6	Measure the voltage of the FTP 5-volt reference circuit with a DMM. Refer to Circuit Testing in Wiring Systems. Is the Fuel Tank Pressure Sensor parameter within the specified value?	4.8-5.2 V	Go to Step 9	Go to Step 10
7	Test the FTP signal circuit for a short to voltage or for a short to a 5-volt reference circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 13	Go to Step 12
8	Test for an intermittent and for a poor connection at the control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 13	Go to Step 12
9	Test for an intermittent and for a poor connection at the FTP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 13	Go to Step 11
10	Repair the short to voltage in the FTP 5-volt reference circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair?		Go to Step 13
11	Replace the FTP sensor. Refer to Fuel Tank Pressure Sensor Replacement . Did you complete the replacement?		Go to Step 13
12	Replace the powertrain control module (PCM). Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement?		Go to Step 13
13	Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition?		Go to Step 2	Go to Step 14
14	Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed?		Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information	System OK

DTC P0453

The control module tests the Evaporative Emission (EVAP) System for a large leak. The control module monitors the fuel tank pressure (FTP) sensor signal to determine the EVAP system vacuum level. When the conditions for running are met, the control module commands the EVAP canister purge solenoid valve OPEN and the EVAP vent solenoid valve CLOSED. This allows engine vacuum to enter the EVAP system. At a calibrated time, or vacuum level, the control module commands the EVAP canister purge solenoid valve closed, sealing the system, and monitors the FTP sensor input in order to determine the EVAP system vacuum level. If the system is unable to achieve the calibrated vacuum level, or the vacuum level decreases too rapidly, this DTC sets.

The following table illustrates the relationship between the ON and OFF states, and the OPEN or CLOSED states of the EVAP canister purge and vent solenoid valves.

Control Module Command	EVAP Canister Purge Solenoid Valve	EVAP Canister Vent Solenoid Valve
ON	Open	Closed
OFF	Closed	Open

DTC P0455

The numbers below refer to the step numbers on the diagnostic table.

3: This test verifies that the EVAP canister purge solenoid valve is electrically functional.
4: This test verifies that the EVAP canister vent solenoid valve is electrically functional.
9: Introducing smoke in 15 second intervals may allow smaller leak areas to be more noticeable. When the system is less pressurized, the smoke will sometimes escape in a more condensed manner.
11: This test verifies that the FTP sensor is accurate. An FTP sensor that does not correctly respond to vacuum, or pressure may cause this DTC to set.

Step	Action	Values	Yes	No
Schematic Reference: Engine Controls Schematics or Evaporative Emissions (EVAP) Hose Routing Diagram Connector End View Reference: Powertrain Control Module (PCM) Connector End Views or Engine Controls Connector End Views
1	Did you perform the Diagnostic System Check - Vehicle?		Go to Step 2	Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2	Inspect the evaporative emission (EVAP) system for the following conditions: A loose, missing, or damaged service port Schrader valve A loose, incorrect, missing, or damaged fuel fill cap A damaged EVAP canister purge solenoid valve Raise the vehicle on a hoist. Refer to Lifting and Jacking the Vehicle in General Information. Inspect the EVAP system for the following conditions: Any disconnected, improperly routed, kinked, or damaged EVAP pipes and hoses A damaged EVAP canister vent solenoid valve or EVAP canister Did you find and correct the condition?		Go to Step 34	Go to Step 3
3	Clear the DTCs with a scan tool. Command the EVAP canister purge solenoid valve to 50 percent and back to 0 percent with a scan tool. Do you hear or feel a clicking from the EVAP canister purge solenoid valve when it is commanded to 50 percent?		Go to Step 4	Go to Step 5
4	Command the EVAP canister vent solenoid valve ON and OFF with the scan tool. Do you hear or feel a click as the EVAP canister vent solenoid valve is commanded ON and OFF?		Go to Step 9	Go to Step 7
5	Disconnect the EVAP canister purge solenoid valve. Turn ON the ignition, with the engine OFF. Connect a test lamp between the ignition 1 voltage circuit of the EVAP canister purge solenoid valve and a known good ground. Refer to Troubleshooting with a Test Lamp in Wiring Systems. Does the test lamp illuminate?		Go to Step 6	Go to Step 25
6	Connect a test lamp between the ignition 1 voltage circuit of the EVAP canister purge solenoid valve and the control circuit of the EVAP purge solenoid. Refer to Circuit Testing in Wiring Systems. Command the EVAP canister purge solenoid valve to 50 percent and then to 0 percent with a scan tool. Does the test lamp illuminate or pulsate when the EVAP canister purge solenoid valve is commanded to 50 percent and turn OFF when the EVAP canister purge solenoid valve is commanded to 0 percent?		Go to Step 20	Go to Step 18
7	Turn ON the ignition, with the engine OFF. Disconnect the EVAP canister vent solenoid valve. Connect a test lamp between the ignition 1 voltage circuit of the EVAP canister vent solenoid valve and a known good ground. Refer to Troubleshooting with a Test Lamp in Wiring Systems. Does the test lamp illuminate?		Go to Step 8	Go to Step 26
8	Connect a test lamp between the ignition 1 voltage circuit of the EVAP canister vent solenoid valve and the control circuit of the EVAP canister vent solenoid valve. Refer to Troubleshooting with a Test Lamp in Wiring Systems. Command the EVAP canister vent solenoid valve ON, with a scan tool. Does the test lamp illuminate?		Go to Step 21	Go to Step 19
9	IMPORTANT: Ensure that the vehicle underbody temperature is similar to the ambient temperature and allow the surrounding air to stabilize before starting the diagnostic procedure. System flow will be less with higher temperatures. Turn OFF the ignition. Connect the J 41413-200 Evaporative Emissions System Tester (EEST) power supply clips to a known good 12-volt source. See Special Tools . Install the J 41415-40 Fuel Tank Cap Adapter to the fuel fill pipe. See Special Tools . Connect the fuel fill cap to the J 41415-40 . See Special Tools . Connect the J 41413-200 nitrogen/smoke supply hose to the J 41415-40 . See Special Tools . Turn ON the ignition, with the engine OFF. Command the EVAP canister vent solenoid valve closed with a scan tool. Turn the nitrogen/smoke valve on the J 41413-200 control panel to SMOKE. See Special Tools . Use the remote switch to introduce smoke into the EVAP system. Use the J 41413-VLV EVAP Service Port Vent Fitting to open the EVAP service port. See Special Tools . Remove the J 41413-VLV once smoke is observed. See Special Tools . Continue to introduce smoke into the EVAP system for an additional 60 seconds. Inspect the entire EVAP system for exiting smoke with the J 41413-SPT High Intensity White Light. See Special Tools . Continue to introduce smoke at 15 second intervals until the leak source has been located. Did you locate and repair a leak source?		Go to Step 34	Go to Step 10
10	Disconnect the J 41415-40 from the fuel fill pipe. See Special Tools . Install the fuel fill cap to the fuel fill pipe. Connect the J 41413-200 nitrogen/smoke supply hose to the EVAP service port. See Special Tools . Use the remote switch to introduce smoke into the EVAP system. Inspect the entire EVAP system for exiting smoke with the J 41413-SPT . See Special Tools . Continue to introduce smoke at 15 second intervals until the leak source has been located. Did you locate and repair a leak source?		Go to Step 34	Go to Step 11
11	Use the remote switch to stop introducing smoke. Install the J 41415-40 to the fuel fill pipe. See Special Tools . Connect the J 41413-200 nitrogen/smoke supply hose to the J 41415-40 . See Special Tools . Connect the vehicle fuel fill cap to the J 41415-40 . See Special Tools . Command the EVAP canister vent solenoid valve open with a scan tool. Compare the Fuel Tank Pressure Sensor parameter with a scan tool, to the J 41413-200 pressure/vacuum gage. See Special Tools . Is the scan tool Fuel Tank Pressure Sensor parameter within the specified value of the J 41413-200 pressure/vacuum gage?. See Special Tools .	1 in H2O	Go to Step 12	Go to Step 22
12	Seal the EVAP system using the EVAP Purge/Seal function with a scan tool. Turn the nitrogen/smoke valve on the J 41413-200 control panel to NITROGEN. See Special Tools . Use the J 41413-200 to pressurize the EVAP system to the first specified value. See Special Tools . Is the Fuel Tank Pressure Sensor parameter more than the second specified value?	10 in H2O 5 in H2O	Go to Step 13	Go to Step 22
13	Use the remote switch to stop introducing nitrogen into the EVAP system. Increase the EVAP canister purge solenoid valve to 100 percent. Is the Fuel Tank Pressure Sensor parameter Less than the specified value?	1 in H2O	Go to Diagnostic Aids	Go to Step 14
14	Disconnect the EVAP purge vacuum source from the EVAP canister purge solenoid valve. Is the Fuel Tank Pressure Sensor parameter less than the specified value?	1 in H2O	Go to Step 24	Go to Step 15
15	Disconnect the EVAP purge pipe from the EVAP canister purge solenoid valve. Is the Fuel Tank Pressure Sensor parameter Less than the specified value?	1 in H2O	Go to Step 29	Go to Step 16
16	Disconnect the EVAP purge pipe at the EVAP canister. Is the Fuel Tank Pressure Sensor parameter Less than the specified value?	1 in H2O	Go to Step 27	Go to Step 17
17	Disconnect the EVAP vapor pipe at the EVAP canister. Is the Fuel Tank Pressure Sensor parameter Less than the specified value?	1 in H2O	Go to Step 31	Go to Step 28
18	Test the control circuit of the EVAP canister purge solenoid valve for an open or for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 34	Go to Step 23
19	Test the control circuit of the EVAP canister vent solenoid valve for an open or for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 34	Go to Step 23
20	Test for an intermittent and for a poor connection at the EVAP canister purge solenoid valve. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 34	Go to Step 29
21	Test for an intermittent and for a poor connection at the EVAP canister vent solenoid valve. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 34	Go to Step 30
22	Test for an intermittent and for a poor connection at the fuel tank pressure (FTP) sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 34	Go to Step 32
23	Test for an intermittent and for a poor connection at the control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 34	Go to Step 33
24	Repair the pinched or obstructed EVAP canister purge solenoid valve vacuum source. Did you complete the repair?		Go to Step 34
25	Repair the open or short to ground in the ignition 1 voltage circuit of the EVAP canister purge solenoid valve. Refer to Wiring Repairs in Wiring Systems. Replace the fuse as necessary. Did you complete the repair?		Go to Step 34
26	Repair the open or short to ground in the ignition 1 voltage circuit of the EVAP canister vent solenoid valve. Refer to Wiring Repairs in Wiring Systems. Replace the fuse as necessary. Did you complete the repair?		Go to Step 34
27	Repair the restriction in the EVAP purge pipe. Refer to Evaporative Emission (EVAP) System Cleaning . Did you complete the repair?		Go to Step 34
28	Repair the restriction in the EVAP vapor pipe. Did you complete the repair?		Go to Step 34
29	Replace the EVAP canister purge solenoid valve. Refer to Evaporative Emission (EVAP) Canister Purge Solenoid Valve Replacement . Did you complete the replacement?		Go to Step 34
30	Replace the EVAP canister vent solenoid valve. Refer to Evaporative Emission (EVAP) Canister Vent Solenoid Valve Replacement . Did you complete the replacement?		Go to Step 34
31	Replace the EVAP canister. Refer to Evaporative Emission (EVAP) Canister Replacement (TrailBlazer, Envoy, Rainier) or Evaporative Emission (EVAP) Canister Replacement (Trailblazer EXT, Envoy XL, Envoy XUV) . Did you complete the replacement?		Go to Step 34
32	Replace the FTP sensor. Refer to Fuel Tank Pressure Sensor Replacement . Did you complete the replacement?		Go to Step 34
33	Replace the powertrain control module (PCM). Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement?		Go to Step 34
34	IMPORTANT: Larger volume fuel tanks and/or those with lower fuel levels may require several minutes for the floating indicator to stabilize. Turn the nitrogen/smoke valve to nitrogen. Connect the nitrogen/smoke hose to the 0.5 mm (0.20 in) test orifice on the bottom-front of the J 41413-200 . See Special Tools . Use the remote switch to activate the J 41413-200 . See Special Tools . Align the red flag on the flow meter with the floating indicator. Use the remote switch to de-activate the J 41413-200 . See Special Tools . Install the J 41415-40 to the fuel fill pipe. See Special Tools . Remove the nitrogen/smoke hose from the test orifice and install the hose onto the J 41415-40 . See Special Tools . Turn ON the ignition, with the engine OFF. Command the EVAP canister vent solenoid valve closed with a scan tool. Use the remote switch to introduce nitrogen and fill the EVAP system until the floating stabilizes. Compare the flow meter's stable floating indicator position to the red flag. Is the floating indicator below the red flag?	5 in H2O	Go to Step 35	Go to Step 2
35	Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed?		Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information	System OK

IMPORTANT
Ensure that the vehicle underbody temperature is similar to the ambient temperature and allow the surrounding air to stabilize before starting the diagnostic procedure. System flow will be less with higher temperatures.

IMPORTANT
Larger volume fuel tanks and/or those with lower fuel levels may require several minutes for the floating indicator to stabilize.

DTC P0455

This DTC tests for undesired intake manifold vacuum flow to the evaporative emission (EVAP) system. The control module seals the EVAP system by commanding the EVAP canister purge solenoid valve Closed and the EVAP canister vent solenoid valve Closed. The control module monitors the fuel tank pressure (FTP) sensor to determine if a vacuum is being drawn on the EVAP system. If vacuum in the EVAP system is more than a predetermined value within a predetermined time, this DTC sets.

The following table illustrates the relationship between the ON and OFF states, and the Open or Closed states of the EVAP canister purge and vent solenoid valves.

Control Module Command	EVAP Canister Purge Solenoid Valve	EVAP Canister Vent Solenoid Valve
ON	Open	Closed
OFF	Closed	Open

DTC P0496

The numbers below refer to the step numbers on the diagnostic table.

2: This step inspects for a leaking EVAP canister purge solenoid valve.
4: Removing the fuel fill cap will equalize the pressure inside the tank with atmospheric pressure. At 0 inches of H2O the FTP sensor should be near 1.5 volts. If the sensor is not, there is a concern with the sensor or related wiring.

Step	Action	Values	Yes	No
Schematic Reference: Evaporative Emissions (EVAP) Hose Routing Diagram and Engine Controls Schematics Connector End View Reference: Powertrain Control Module (PCM) Connector End Views or Engine Controls Connector End Views
1	Did you perform the Diagnostic System Check - Vehicle?		Go to Step 2	Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2	Disconnect the purge pipe from the evaporative emission (EVAP) canister purge solenoid valve. Install a hand held vacuum gage to the EVAP canister purge solenoid valve purge port. Disconnect the EVAP canister purge solenoid valve harness connector. Monitor vacuum on the vacuum gage. Start the engine and allow the engine to idle. Increase the idle to 1,200-1,500 RPM. Does the vacuum gage indicate an increase in vacuum?		Go to Step 8	Go to Step 3
3	Connect the EVAP canister purge solenoid valve harness connector. Monitor vacuum on the vacuum gage. Increase the idle to 1,200-1,500 RPM. Does the vacuum gage indicate an increase in vacuum?		Go to Step 5	Go to Step 4
4	Turn OFF the ignition. Remove and then install the fuel fill cap. Turn ON the ignition, with the engine OFF. Observe the Fuel Tank Pressure Sensor parameter with a scan tool. Is the Fuel Tank Pressure Sensor parameter within the specified value?	0.5 to +0.5 in H2O	Go to Diagnostic Aids	Go to Step 6
5	Test the control circuit of the EVAP canister purge solenoid valve for a short to ground. Refer to Testing for Short to Ground and Wiring Repairs in Wiring Systems. Did you find and correct the conditions?		Go to Step 9	Go to Step 8
6	Test for an intermittent and for a poor connection at the fuel tank pressure (FTP) sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?		Go to Step 9	Go to Step 7
7	Replace the FTP sensor. Refer to Fuel Tank Pressure Sensor Replacement . Did you complete the replacement?		Go to Step 9
8	Replace the EVAP canister purge solenoid valve. Refer to Evaporative Emission (EVAP) Canister Purge Solenoid Valve Replacement . Did you complete the replacement?		Go to Step 9
9	Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition?		Go to Step 2	Go to Step 10
10	Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed?		Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information	System OK

DTC P0496

The number below refers to the step number on the diagnostic table.

2: This test determines whether the engine can achieve the commanded RPM. If the engine does not reach the commanded RPMs, the test determines whether the RPM is too high or too low.

Step	Action	Yes	No
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module (PCM) Connector End Views or Engine Controls Connector End Views
1	Did you perform the Diagnostic System Check - Vehicle?	Go to Step 2	Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2	Start the engine. Command the engine speed up to 1,500 RPM, down to 500 RPM, and up to 1,500 RPM, with a scan tool. Exit the RPM control function. Does the engine speed correspond, within 100 RPM, with each command?	Go to Intermittent Conditions	Go to Step 3
3	Inspect for any condition that can reduce idle speed by increasing engine load. Examples include: Incorrect torque converter clutch (TCC) operation Accessories that require additional torque to operate Restricted exhaust Mechanical conditions that limit engine speed Did you complete the action?	Go to Step 4
4	Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition?	Go to Step 2	Go to Step 5
5	Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed?	Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information	System OK

DTC P0506

Engine Control System - 4.2L - DTC P0140 to P0506: Overview GMC Envoy II

Test Description

System Description

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