Engine Control System - Self-Diagnostics: Overview Pontiac Vibe I

Description

The Diagnostic System Check - Engine Controls is an organized approach to identifying a condition that is created by a malfunction in the engine control system. The diagnostic system check must be the starting point for any driveability concern. The diagnostic system check directs the service technician to the next logical step to diagnose the concern. Understanding and correctly using the diagnostic procedure reduces diagnostic time and prevents replacement of good parts.

Test Description

The numbers below refer to the step numbers in the diagnostic procedure.

1. 2 - Lack of communication may be due to a malfunction of the serial data circuit, control module, or scan tool. This step will determine the particular condition.
2. 5 - This step stores the PCM DTC information into the scan tool memory. Review the captured information at the end of the diagnostic procedure to catch the next DTC in the event there are multiple DTCs stored. Use this information to determine how frequently and how recently the DTC set. This information and other operating conditions when the DTC set may help diagnose an intermittent condition. Capturing stored information preserves data the PCM loses when the following occurs: When instructed to clear DTCs. PCM connectors are disconnected. PCM is replaced during a diagnostic procedure or a repair procedure.
3. 6 - A DTC P1600 that is stored must be diagnosed first. If multiple powertrain DTCs are stored, diagnose in the following order of priority: Component Level DTCs - Sensors, solenoids, relays etc. Multiple DTCs within this category should be diagnosed in numerical order starting with the lowest numbered DTC, unless otherwise directed. System Level DTCs - Misfire, fuel trim, catalyst etc.
4. 8 - This step is for vehicles that are located in areas that have an Inspection/Maintenance or emission testing program. The testing facility found one or more I/M system statuses not set.

Several states require that a vehicle pass On-Board Diagnostic (OBD) system tests and I/M emission inspection to renew license plates. This is accomplished by viewing I/M SYSTEM STATUS display on scan tool. Using a scan tool, the technician can observe the I/M System Status to verify that vehicle meets the criteria that complies with the local area requirements.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 1 - Any DTCs set, even those that are not listed in the Inspection/Maintenance System DTCs, may prevent the required DTCs from running. If there is any question as to whether a set DTC is disabling the required I/M diagnostic, review Conditions for Running in the diagnostic procedures for the DTC required by the I/M diagnostic. A list of disabling DTCs, if applicable, is contained in the supporting text for that DTC.
2. 2 - Anytime a control module is reprogrammed or the diagnostic trouble codes are cleared as part of a repair procedure, all I/M SYSTEM STATUS indicators will reset to NO.
3. 3 - Use discretion when determining whether the entire system set procedure needs to be performed. For example, if the only tests that have not run are those that require the engine to be at operating temperature, then only those individual tests need to be run. There is no need to allow the engine to completely cool to run these tests.

The purpose of I/M Complete System Set Procedure is to satisfy the enable criteria necessary to execute all I/M readiness diagnostics, and complete the trips for those particular diagnostics. When all diagnostic tests are completed, I/M SYSTEM STATUS indicators are set to YES. Perform this test when more than one or all I/M System Status indicators are set to NO.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 1 - Ensure you perform the I/M System Check before performing this test. Failure to do so may result in difficulty updating status to YES. See «INSPECTION/MAINTENANCE SYSTEM CHECK»(ref-152429-S16683892272003020400000) .
2. 2 - This step runs HO2S Heater Tests and initiate the EVAP System Test.
3. 3 - This step is to run the catalyst test. The catalyst test runs during the specified cruise period.
4. 4 - This step is to set up the Oxygen Sensor (O2S) tests. These tests run during the idle period immediately following a cruise period that meets a minimum calibrated RPM and time period.
5. 5 - This step is to run the oxygen sensor tests and EVAP Tests. These tests run during the idle period immediately following a cruise period that meets a minimum calibrated RPM and time period.
6. 6 - Perform individual system test for any systems that do not update to YES.
7. 7 - I/M SYSTEM STATUS only reports on whether or not a diagnostic has run, not the outcome of the test. If any emission related DTC sets after the tests are complete, the DTC will require diagnosis.

The following DTCs are required to set system status to YES

Catalyst System

1. P0420 - Catalyst System Low Efficiency

EVAP System

1. P0440 - EVAP System
2. P0441- EVAP System No Flow During Purge
3. P0442 - EVAP System Small Leak Detected
4. P0446 - EVAP System Vent System Performance

Oxygen Sensor System

1. P0130 - HO2S 1 Circuit
2. P0133 - HO2S 1 Slow Response

Oxygen Sensor Heater System

1. P0135 Or P0141- HO2S 1 Heater Performance

Diagnose affected DTCs. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .

The purpose of this test is to satisfy the enable criteria necessary to execute I/M readiness diagnostics for the catalyst system. Test may be used to set the I/M System Status indicators to YES. Ensure vehicle meets requirements listed in conditions for running before performing this test. See CONDITIONS FOR RUNNING . Failure to meet necessary requirements may produce inaccurate test results.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 1 - Ensure you perform the I/M system check before performing this test. Failure to do so may result in difficulty updating status to YES.
2. 2 - The catalyst test runs during the specified cruise period.
3. 3 - This step is to identify a first failure of a type "B" DTC. A DTC only appears on the I/M system status display when DTC becomes a MIL illuminating DTC. This occurs on the second failure of a type "B" DTC. A first failure of a type "B" DTC will not allow the I/M system status to update to YES. See «DIAGNOSTIC AIDS»(ref-152429-S37567827172003020400000) .
4. 4 - This step helps identify any unique or any unusual criteria required to run the diagnostic test in the event the universal set procedure does not. This information is located in the service information under conditions for running the DTC. See «CONDITIONS FOR RUNNING»(ref-152429-S34499496422003020400000) .
5. 5 - I/M system status only reports on whether or not a diagnostic has run, not the outcome of the test. If any emission related DTC sets after tests are complete, the DTC will require diagnosis.

The purpose of this test is to satisfy enable criteria necessary to execute I/M readiness diagnostics for the EVAP system. The test may be used to set I/M system status indicators to YES. Service Bay Tests are included on the scan tool for some systems depending upon vehicle make and model. The test is designed to allow the EVAP diagnostic tests to run in service bay conditions. Ensure the vehicle meets the requirements listed in CONDITIONS FOR RUNNING before performing either EVAP system test. Failure to meet necessary requirements may produce inaccurate test results.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 1 - Ensure you perform the I/M system check before performing this test. Failure to do so may result in difficulty updating status to YES.
2. 2 - EVAP system test runs immediately following the idle period.
3. 3 - This step is to identify a first failure of a type "B" DTC. A DTC only appears on I/M system status display when DTC becomes a MIL illuminating DTC. This occurs on the second failure of a type "B" DTC. A first failure of a type "B" DTC will not allow the I/M system status to update to YES. See «DIAGNOSTIC AIDS»(ref-152429-S35592656262003020400000) .
4. 4 - This step is to help identify any unique or unusual criteria required to run the diagnostic test in the event the universal set procedure does not. This information is located in the service information under conditions for running the DTC.
5. 5 - I/M system status only reports on whether or not a diagnostic has run, not what the outcome of the test was. If any emission related DTC sets after the tests are complete, the DTC will require diagnosis.

The purpose of this test is to satisfy enable criteria necessary to execute I/M readiness diagnostics for the HO2S/O2S system. Test may be used to set I/M system status to YES. Ensure vehicle meets the requirements listed in CONDITIONS FOR RUNNING DTC before performing this test. Failure to meet necessary requirements may produce inaccurate test results.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 1 - Ensure you perform the I/M system check before performing this test. Failure to do so may result in difficulty updating the status to YES.
2. 2 - Oxygen sensor tests begin during the idle period immediately following the cruise period.
3. 3 - This step is to identify a first failure of a type "B" DTC. A DTC only appears on the I/M system status display when it becomes a MIL illuminating DTC. This occurs on the second failure of a type "B" DTC. A first failure of a type "B" DTC will not allow I/M system status to update to YES. See «DIAGNOSTIC AIDS»(ref-152429-S38368729592003020400000) .
4. 4 - This step is to help identify any unique or unusual criteria required to run the diagnostic test in the event the universal set procedure does not. This information is located in the service information under conditions for running DTC. See «CONDITIONS FOR RUNNING»(ref-152429-S24203190532003020400000) .
5. 5 - I/M system status only reports on whether or not a diagnostic has run, not the outcome of the test. If any emission related DTC sets after tests are complete, DTC will require diagnosis.

The purpose of this test is to satisfy enable criteria necessary to execute I/M readiness diagnostics for Heated Oxygen Sensor (HO2S) system. Test may be used to set I/M System Status to YES. Ensure vehicle meets the requirements listed in conditions for running before performing this test. Failure to meet necessary requirements may produce inaccurate test results.

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

1. 1 - Ensure you perform the I/M system check before performing this test. Failure to do so may result in difficulty updating the status to YES.
2. 2 - Preprogramming the scan tool will reduce the amount of time the oxygen sensor heaters operate while verifying the enable criteria. HO2S heater tests may not complete when initiated from a cold start and may require running under a load to complete the tests.
3. 3 - This step is to identify a first failure of a type "B" DTC. A DTC only appears on the I/M SYSTEM STATUS display when it becomes a MIL illuminating DTC. This occurs on the second failure of a type "B" DTC. A first failure of a type "B" DTC will not allow I/M system status to update to YES. Refer to «DIAGNOSTIC AIDS»(ref-152429-S38368729592003020400000) .
4. 4 - This step is to help identify any unique or unusual criteria required to run the diagnostic test in the event the universal set procedure does not. This information is located in the service information under conditions for running the DTC. See «CONDITIONS FOR RUNNING»(ref-152429-S14837094872003020400000) .
5. 5 - The I/M system status only reports on whether or not a diagnostic has run, not the outcome of the test. If any emission related DTC sets after tests are complete, the DTC will require diagnosis.

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

1. 2 - This step checks whether there is communication between PCM and a scan tool device. If PCM is unable to provide serial data to the scan tool, there will be no MIL control.
2. 3 - If other Instrument Panel Cluster (IPC) functions are not working correctly check for an open GAUGE fuse or for a lack of power and ground to IPC.
3. 4 - This step checks for an open MIL control circuit or for an internal PCM failure.
4. 5 - An open fuse determines if a voltage is constantly being applied to the control circuit.

MIL Illumination

1. MIL will illuminate with ignition switch in RUN position and engine not running.
2. MIL will turn OFF when engine is started.
3. MIL will remain illuminated if self-diagnostic system has detected a malfunction.
4. MIL may turn OFF if malfunction is not present.
5. If MIL is illuminated and then the engine stalls, MIL will remain illuminated so long as the ignition switch is in RUN position.
6. If MIL is not illuminated and engine stalls, MIL will not illuminate until the ignition switch is cycled OFF, then to RUN position.

Perform the Diagnostic System Check - Engine Controls, when the following conditions are present

1. MIL does not illuminate when ignition switch is turned to RUN position. See «MIL OPERATION»(ref-152429-S32651728912003020400000) .
2. MIL remains illuminated while engine is running.
3. MIL is flashing while engine is running.
4. A driveability symptom is determined.

The number(s) below refers to the step number on the diagnostic procedures.

1. 1 - The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store freeze frame data, if applicable. This creates an electronic copy of data taken when fault occurred. Information is then stored in the scan tool for later reference.
2. 2 - Disconnecting PCM will determine whether malfunction is caused by a short to ground in MIL control circuit or a faulty PCM.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 1 - The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store freeze frame data, if applicable. This creates an electronic copy of data taken when fault occurred. The information is then stored in the scan tool for later reference.
2. 2 - This step checks for a high input signal from Mass Air Flow (MAF) sensor.
3. 3 - This step checks for a low input signal from MAF sensor.
4. 6 - This step is looking for MAF sensor output on MAF signal high circuit. Air movement around the sensor's hot wire element can cause some fluctuation in the voltage being measured.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 1 - The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store freeze frame data, if applicable. This creates an electronic copy of data taken when fault occurred. Information is then stored in the scan tool for later reference.
2. 4 - This step checks whether DTC P0101 is the result of a hard failure or an intermittent condition. Operating vehicle in check mode enhances the PCM's diagnostic capabilities. For additional information on check mode operation, see «CHECK MODE»(ref-152429-S33295722242003021000000) under SERVICE BAY TESTS under SELF-DIAGNOSTIC SYSTEM.
3. 5 - This step checks for faults in MAF sensor electrical circuits that can cause the PCM to receive incorrect voltage signals. Normal MAF sensor signal on a warm engine at idle is 1.7-2.1 g/s.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 1 - The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store freeze frame data, if applicable. This creates an electronic copy of data taken when fault occurred. Information is then stored in scan tool for later reference.
2. 2 - This step checks for a high input condition. If scan tool reads 284°F (140°C), the input circuit may shorted to the sensor ground circuit.
3. 3 - This step checks for a low input condition. If scan tool reads -40°F (-40°C) the input circuit may be open.
4. 4 - This step checks whether DTC P0110 is the result of a hard failure or an intermittent condition. Operating vehicle in check mode enhances PCM diagnostic capabilities.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 1 - The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and stores freeze frame data, if applicable. This creates an electronic copy of data taken when fault occurred. Information is then stored on the scan tool for later reference.
2. 2 - This step checks for a high input condition. If scan tool reads 284°F (140°C), input circuit results may be the result of a short circuit.
3. 3 - This step checks for a low input condition. If scan tool reads -40°F (-40°C), input circuit results may be the result of an open circuit.
4. 4 - This step determines if DTC P0115 is the result of a hard failure or an intermittent condition.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 1 - The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store freeze frame data on the scan tool, if applicable. This creates an electronic copy of data taken when fault occurred. The information is then stored for later reference.
2. 3 - This step checks for a faulty ECT sensor or ECT sensor circuit.
3. 4 - This step checks integrity of ECT sensor input circuit.
4. 5 - This step checks integrity of ECT sensor ground circuit.
5. 6 - This step checks integrity of ECT sensor input circuit.
6. 11 - A cooling system that prevents engine from warming up properly and reaching the correct engine operating temperature within a set run time can cause a DTC P0116 to set. A thermostat that stays open slightly can cause a DTC P0116 to set in cold weather when vehicle is started and let sit while warming up. Replace thermostat if suspect.
7. 12 - This step determines if DTC P0116 is result of a hard failure or an intermittent condition.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 1 - The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store freeze frame data on the scan tool, if applicable. This creates an electronic copy of data taken when the fault occurred. The information is then stored in scan tool for later reference.
2. 2 - This step determines if DTC P0120 is the result of a hard failure or an intermittent condition.
3. 7 - When the 5-volt reference is jumpered to TP input circuit, scan tool parameter should read 99 percent.
4. 8 - When TP sensor input circuit is jumpered to battery voltage, scan tool parameter should read 99 percent.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 1 - The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store freeze frame data, if applicable. This creates an electronic copy of data taken when fault occurred. Information is then stored in scan tool for later reference.
2. 2 - Throttle angle percentage should steadily increase without binding or a large percentage jump.
3. 3 - This step determines if DTC P0121 is the result of a hard failure or an intermittent condition.
4. 4 - This step determines if DTC P0121 is the result of a hard failure or an intermittent condition.
5. 5 - This step inspects for excessive resistance in reference voltage circuit. If test light does not illuminate at all, there is resistance in the circuit.
6. 7 - When 5-volt reference circuit is jumpered to TP sensor input circuit, scan tool parameter should read near 100 percent.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 1 - The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and stores freeze frame data, if applicable. This creates an electronic copy of data taken when fault occurred. Information is then stored on scan tool for later reference.
2. 3 - This step verifies whether malfunction is a hard failure or an intermittent.
3. 4 - This step verifies whether PCM is able to receive a signal from the HO2S 1. DMM is used as a low current voltage source taking place of the HO2S.
4. 8 - A condition that affects fuel mixture or combustion event in the engine can impact operation of the HO2S. This can cause an accurate signal from HO2S to fail the diagnostic. Performing tests listed in Diagnostic Aids will eliminate a faulty running condition and prevent replacement of a good oxygen sensor.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 1 - The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store freeze frame data on the scan tool if applicable. This creates an electronic copy of data taken when fault occurred. Information is then stored in scan tool for later reference.
2. 2 - This step compares the ECT temperature to IAT temperature. This inspection is to be performed when vehicle has reached ambient room temperature. At that time both surrounding air temperature and engine coolant temperature are nearly equal. If ECT sensor and circuit are OK, both sensors should indicate the same temperature.
3. 3 - This step checks temperature of engine coolant increases at least 36°F (20°C) within 10 minutes. If temperature does not increase at least 38°F (20°C) there is a fault with ECT sensor or engine cooling system.
4. 6 - Fault not present indicates the condition that caused DTC P0128 to set is intermittent and not currently present. If no other DTCs are stored, refer to «DIAGNOSTIC AIDS»(ref-152429-S04758786592003020400000) for additional information on diagnosing an intermittent DTC P0128.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 1 - The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store freeze frame data, if applicable. This creates an electronic copy of the data taken when fault occurred. Information is then stored in scan tool for later reference.
2. 2 - This step verifies whether malfunction is presently occurring.
3. 3 - This step checks whether malfunction that caused DTC P0130 is still present. Operating vehicle in CHECK MODE enhances diagnostic capabilities of PCM. HO2S 1 diagnostic can be monitored on scan tool under I/M System Information selection. When HO2S test displays a YES status, indicating that heated oxygen sensor system diagnostic is completed, check for DTC P0130 in LAST TEST FAILED screen of scan tool. If there is no DTC P0130 displayed, HO2S diagnostic has run and passed, indicating that no malfunction was present this time. DTCs MUST be cleared to view CURRENT STATUS of system diagnostics being performed. Do not forget I/M System Information tests only indicate that the test has run, not whether the test passed or failed. LAST TEST FAILED screen must be checked for related DTCs to determine the outcome of the diagnostic test involved.
4. 4 - In this step DMM is used as a low current voltage source taking the place of HO2S. This step verifies whether PCM is able to receive and process a signal from HO2S 1.
5. 8 - A condition that affects fuel mixture or combustion event in the engine can impact the operation of HO2S. This can cause an accurate signal from HO2S to fail the diagnostic. Performing tests listed in «DIAGNOSTIC AIDS»(ref-152429-S29076729212003021300000) will eliminate a faulty running condition and prevent replacement of a good oxygen sensor.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 1 - The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store freeze frame data, if applicable. This creates an electronic copy of data taken when fault occurred. Information is then stored in the scan tool for later reference.
2. 2 - This step checks whether the malfunction that caused the DTC P0133 is still present. Operating vehicle in CHECK MODE enhances the diagnostic capabilities of the PCM. HO2S 1 diagnostic can be monitored on the scan tool under I/M SYSTEM INFORMATION. When HO2S test displays a YES status, indicating the heated oxygen sensor system diagnostic is completed, check for a DTC P0133 in LAST TEST FAILED screen of scan tool. If there is no DTC P0133 displayed the HO2S diagnostic has run and passed, indicating no malfunction was present this time. DTCs MUST be cleared to view CURRENT STATUS of system diagnostics being performed. Do not forget the I/M System Information tests only indicates that the test has run, not whether test passed or failed. LAST TEST FAILED screen must be checked for related DTCs to determine the outcome of the diagnostic test involved.
3. 5 - In this step, DMM is used as a low current voltage source taking the place of the HO2S. This step verifies whether PCM is able to receive and process a signal from the HO2S 1.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 1 - The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store freeze frame data, if applicable. This creates an electronic copy of data taken when fault occurred. Information is then stored in the scan tool for later reference.
2. 2 - This step checks whether the malfunction that caused DTC P0135 or P0141 is still present. Operating vehicle in check mode enhances diagnostic capabilities of PCM. HO2S heater diagnostic can be monitored on scan tool under I/M SYSTEM INFORMATION selection of SYSTEM INFORMATION. When HO2S Heater test displays a YES status, indicating the oxygen sensor heater diagnostic is completed, check for a DTC P0135 or P0141 in LAST TEST FAILED screen of the scan tool. If there is no DTC P0135 or P0141 displayed, HO2S heater diagnostic has run and passed, indicating no malfunction was present this time. DTCs MUST be cleared to view CURRENT STATUS of the system diagnostics being performed. Do not forget that I/M System Information tests only indicate that test has run, not whether test passed or failed. LAST TEST FAILED screen must be checked for related DTCs to determine the outcome of the diagnostic test involved.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 1 - The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store freeze frame data, if applicable. This creates an electronic copy of data taken when fault occurred. The information is then stored in scan tool for later reference.
2. 2 - This step checks whether malfunction is a high input condition.
3. 3 - In this step, DMM is used as a low current voltage source taking the place of the HO2S.
4. 4 - This step checks whether malfunction is a low input condition.
5. 5 - This step determines if DTC P0136 is the result of a hard failure or an intermittent condition.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 3 - HO2S 2 voltage may default to Bias voltage. The DTC should be cleared and freeze frame/failure records data recorded before proceeding. A normally functioning HO2S 2 voltage signal will fluctuate greater than and less than bias voltage amount. The action in the test step should result in a visible reaction from HO2S 2 output.
2. 5 - A voltage reading other than bias voltage in this step indicates a short circuit condition in the high signal circuit.
3. 7 - Conditions listed in the table may contribute to failure of HO2S. Conditions listed apply only to this type of failure.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 2 - HO2S 2 voltage may default to bias voltage. DTC should be cleared and freeze frame/failure records data recorded before proceeding. A normally functioning HO2S 2 voltage signal will fluctuate greater than and less than bias voltage amount. Action in test step should result in a visible reaction from HO2S 2 output.
2. 4 - A voltage reading other than specified amount in this step indicates an open circuit condition in one of the signal circuits or PCM.
3. 5 - This step inspects for an open circuit condition in signal circuits, independent of PCM.
4. 7 - The conditions listed in the table may contribute to failure of HO2S. Conditions listed apply only to this type of failure.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 2 - HO2S 2 should be allowed to cool before performing this test. HO2S 2 is cool enough if voltage output is stable at bias or about 450 mV. If HO2S 2 heater is functioning, signal voltage will gradually change as sensor element warms. If heater is not functioning, HO2S 2 signal will remain near 450 mV bias voltage or show very little activity.
2. 4 - This step ensures that ignition voltage circuit to HO2S 2 is not open or shorted. Test light must be connected to a good ground, independent of HO2S system.
3. 6 - This test must not be performed until HO2S 2 heater has cooled and stabilized for at least 15 minutes. Heater resistance is typically about 5 ohms at room temperature.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 1 - The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store freeze frame data, if applicable. This creates an electronic copy of data taken when fault occurred. The information is then stored in the scan tool for later reference.
2. 3 - Visually and physically checking items that may cause a lean condition that may determine the reason the DTC set.
3. 4 - Engine control sensors that are found to be out range (skewed) or fixed, can cause the engine to run lean. Go to the applicable sensor DTC diagnostic procedure for direction in diagnosing any possible sensor error. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000)
4. 6 - Contaminants in the fuel, such as alcohol or water, can create a lean condition and set DTC P0171.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 1 - The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store the freeze frame data, if applicable. This creates an electronic copy of data taken when fault occurred. The information is then stored in the scan tool for later reference.
2. 3 - A plugged air filter can cause a rich condition and set a DTC P0172.
3. 4 - If one of the engine control sensors are found to be out of range (skewed) or stuck, refer to applicable diagnostic table.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 1 - The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store freeze frame data, if applicable. This creates an electronic copy of data taken when fault occurred. Information is then stored in the scan tool for later reference.
2. 2 - This step verifies whether misfire is present. The scan tool will display increasing counts in TOTAL MISFIRE CURRENT COUNT parameter, if a misfire is occurring.
3. 3 - This step checks whether DTC P0300 is the result of a hard failure or an intermittent condition. Operating vehicle in CHECK MODE enhances diagnostic capabilities of PCM. Scan tool will display increasing counts in TOTAL MISFIRE CURRENT COUNT parameter if a misfire is occurring.
4. 4 - Fault not present indicates that condition(s) that caused DTC P0300 to set is intermittent and not currently present. If no other DTCs are stored, refer to «DIAGNOSTIC AIDS»(ref-152429-S05186635862003020400000) for additional information on diagnosing an intermittent DTC P0300.
5. 12 - Contaminants in fuel, such as alcohol or water, can create a misfire condition.
6. 13 - A vacuum leak can cause a lean misfire condition.

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

1. 1 - The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store freeze frame data, if applicable. This creates an electronic copy of data taken when fault occurred. Information is then stored in the scan tool for later reference.
2. 2 - This step verifies whether misfire is present. The scan tool will display increasing counts in MISFIRE CURRENT CYL. NO. data parameter of misfiring cylinder when a misfire is occurring.
3. 3 - This step checks whether MIL is the result of a hard failure or an intermittent condition. Operating vehicle in CHECK MODE enhances the diagnostic capabilities of the PCM. Scan tool will display increasing counts in MISFIRE CURRENT CYL. NO. data parameter of the cylinder that is experiencing a misfire.
4. 4 - Fault not present indicates the condition that caused DTC P0301-P0304 to set is intermittent and not currently present. If no other DTCs are stored, see «DIAGNOSTIC AIDS»(ref-152429-S06840761612003021400000) for additional information on diagnosing an intermittent DTC P0301-P0304.
5. 5 - This step is to verify if the misfire is caused by a fault in the ignition system.
6. 13 - Contaminants in fuel, such as alcohol or water, can create a misfire condition.

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

1. 1 - The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store freeze frame data, if applicable. This creates an electronic copy of data taken when fault occurred. The information is then stored in the scan tool for later reference.
2. 2 - This step verifies whether DTC P0325 is the result of a hard failure or an intermittent condition. Operating vehicle in CHECK MODE enhances diagnostic capabilities of the PCM.
3. 4 - This step verifies resistance of the KS.
4. 5 - This step verifies knock sensors ability to output the correct frequency signal for a given engine speed.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 1 - The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store freeze frame data on scan tool, if applicable. This creates an electronic copy of data taken when fault occurred. Information is then stored in the scan tool for later reference.
2. 3 - This step determines whether DTC P0335 is the result of a hard failure or an intermittent condition. If engine will not start, crank engine over 3 consecutive ignition cycles (key ON - key OFF).
3. 5 - This step verifies internal resistance of the CKP sensor. A typical value at 74°F (23°C) is 2.1 k/ohms.
4. 6 - This step tests CKP sensor output signal and electrical circuit to PCM.
5. 7 - This step determines which half of CKP sensor circuit is faulty.
6. 11 - This step inspects for a faulty signal rotor. Visually check the teeth of the signal rotor through CKP sensor aperture for damage, foreign material, and mis-alignment.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 1 - The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store freeze frame data, if applicable. This creates an electronic copy of data taken when fault occurred. Information is then stored in the scan tool for later reference.
2. 2 - This step tests for an open in CMP sensor ground circuit between PCM connector C1 terminal No. 34 to splice SP108. Engine will not stay running and DTC P0340 will set if CMP sensor and CKP sensor ground circuit is open.
3. 3 - This step determines if DTC P0340 is the result of a hard failure or an intermittent condition.
4. 5 - This step verifies internal resistance of CMP sensor. A typical value at 74°F (23°C) is 1.1 k/ohms.
5. 6 - This step verifies CMP sensor output signal. CMP sensor sends PCM one electrical pulse for every revolution of the intake camshaft. Therefore, the AC signal generated by the CMP sensor will be numerically analogous to engine speed. With engine speed at about 1200 RPM, CMP sensor voltage should be around 2.450-2.5500 volts AC.
6. 8 - This step tests the Camshaft Position (CMP) input circuit to PCM. AC signal generated by CMP sensor will be numerically analogous to engine speed. With engine speed at about 1200 RPM, CMP sensor voltage should be around 2.450-2.550 volts AC. CMP sensor signal wire must be removed from PCM connector to accurately check sensor output. If CMP sensor signal wire is backprobed while connected to PCM, AC voltage indicated on a DMM will be approximately 15-20 percent lower than actual engine speed.
7. 12 - This step inspects for a faulty signal rotor on the camshaft. Visually check the tooth of the signal rotor through the CMP sensor aperture for damage, foreign material, and installation.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 1 - The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store freeze frame data, if applicable. This creates an electronic copy of data taken when fault occurred. The information is then stored in the scan tool for later reference.
2. 3 - This step verifies whether malfunction is presently occurring.
3. 4 - This step checks whether malfunction that caused DTC P0420 is still present. The catalytic converter diagnostic can be monitored on scan tool under I/M SYSTEM INFORMATION. When Catalyst test displays a YES status, indicating the catalytic converter diagnostic is completed, check for DTC P0420 in LAST TEST FAILED screen of scan tool. If there is no DTC P0420 displayed Catalyst diagnostic has run and passed, indicating that no malfunction was present this time. DTCs MUST be cleared to view CURRENT STATUS of system diagnostics being performed. Do not forget the I/M System Information tests only indicate that test has run, not if test passed or failed. LAST TEST FAILED screen must be checked for related DTCs to determine the outcome of the diagnostic test involved.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 3 - This step verifies that the DTC P0440 is captured in freeze frame/failure record list. When multiple EVAP system DTCs are set, the DTC stored in freeze frame/failure record is the best diagnostic starting point.
2. 5 - This test verifies the EVAP purge solenoid is electrically functional.
3. 6 - This test verifies the EVAP vent solenoid is electrically functional.
4. 7 - his test verifies the EVAP pressure switching solenoid is electrically functional
5. 14 - The fuel filler pipe has two vent lines that allow for recirculation of fuel vapors between fuel filler pipe and fuel tank. Because of these vent lines, EEST can be connected to the EVAP service port for leak detection. Waiting until smoke is seen before plugging EVAP canister drain hose speeds up the filling of the canister with smoke. Introducing smoke in between 60 second intervals of Nitrogen will speed up the filling of smoke in the fuel tank and filler pipe vapor space. This occurs because pressure at which Nitrogen gas is applied is greater than pressure at which smoke is introduced. Nitrogen gas pushes the smoke that was just introduced through the canister and into the fuel tank.
6. 15 - This test verifies the Fuel Tank Pressure (FTP) sensor is accurate. An FTP sensor that does not correctly respond to vacuum, or pressure may cause this DTC to set.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 4 - This step verifies EVAP canister purge solenoid electrical operation.
2. 5 - This step tests EVAP canister purge solenoid function.
3. 8 - This step uses EVAP Purge/Seal function to test EVAP canister vent solenoid, pressure switching solenoid, and purge solenoid for correct operation. Using EVAP Purge/Seal function also tests for leaks by allowing the technician to seal the system and monitor FTP sensor.
4. 9 - This step tests EVAP canister vent valve and hoses for a blockage or restriction. If vacuum does not drop to less than -10.0 in. H2O after 30 seconds, there is a faulty condition in EVAP vent system. EVAP vent portion of EVAP control system is diagnosed in DTC P0446.
5. 21 - This step uses EVAP Purge/Seal function to test EVAP canister vent solenoid, pressure switching solenoid, and purge solenoid for correct operation. Using EVAP Purge/Seal function also tests for leaks by allowing the technician to seal the system and monitor FTP sensor.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 3 - This step verifies that DTC P0442 is captured in freeze frame/failure record list. When multiple EVAP system DTCs are set, DTC stored in freeze frame/failure record is the preferred diagnostic starting point.
2. 5 - Fuel filler pipe has two vent lines that allow for recirculation of fuel vapors between fuel filler pipe and fuel tank. Because of these vent lines, EEST can be connected to the EVAP service port for leak detection. Waiting until smoke is seen before plugging EVAP canister drain hose speeds up the filling of the canister with smoke. Introducing smoke in between 60 second intervals of Nitrogen will speed up the filling of smoke in the fuel tank and filler pipe vapor space. This occurs because pressure at which Nitrogen gas is applied is greater than pressure at which smoke is introduced. Nitrogen gas pushes the smoke that was just introduced through the canister and into the fuel tank.
3. 7 - This test verifies that the Fuel Tank Pressure (FTP) sensor is accurate. An FTP sensor that does not correctly respond to vacuum, or pressure may cause this DTC to set.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 3 - This step verifies DTC P0446 is captured in freeze frame/failure record list. When multiple EVAP system DTCs are set, DTC stored in freeze frame/failure record is best diagnostic starting point.
2. 28 - This step uses EVAP Purge/Seal function to test EVAP canister vent solenoid, pressure switching solenoid, and purge solenoid for correct operation. Using EVAP PURGE/SEAL function also tests for leaks by allowing the technician to seal the system and monitor FTP sensor.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 1 - The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store freeze frame data, if applicable. This creates an electronic copy of data taken when fault occurred. The information is then stored in scan tool for later reference.
2. 2 - This step determines if a FTP sensor malfunction is present. Input signal of FTP sensor should indicate atmospheric pressure with fuel tank filler cap removed. FTP sensor will vary with atmospheric pressure. A typical pressure at sea level is 0.0-0.5 in. H2O.
3. 3 - This step determines if DTC P0450 is the result of a hard failure or an intermittent condition. Operating vehicle in CHECK MODE enhances diagnostic capabilities of PCM.
4. 4 - This step checks whether there is trapped negative or positive pressure at FTP sensor.
5. 6 - This step checks for an open or a short in FTP sensor 5-volt reference.
6. 7 - This step checks for an open or short in FTP sensor input circuit.
7. 10 - This step checks for an open in FTP sensor ground circuit.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 1 - The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store freeze frame data, if applicable. This creates an electronic copy of data taken when fault occurred. Information is then stored in scan tool for later reference.
2. 2 - This step determines if a FTP sensor malfunction is present. Input signal of FTP sensor should indicate atmospheric pressure with fuel tank filler cap removed. Fuel tank pressure sensor will vary with atmospheric pressure. A typical pressure at sea level is 0.0-0.5 in. H2O.
3. 3 - This step determines if DTC P0451 is the result of a hard failure or an intermittent condition. Operating vehicle in CHECK MODE enhances diagnostic capabilities of the PCM.
4. 4 - This step determines if there is trapped negative or positive pressure at FTP sensor.
5. 6 - This step inspects for an open or a short in FTP sensor 5-volt reference.
6. 7 - This step inspects for excessive resistance in reference voltage circuit. If test light does not illuminate at all, there is resistance in the circuit.
7. 9 - This step checks for an open or short in FTP sensor input circuit.
8. 11 - This step checks for an open in FTP sensor ground circuit.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 6 - This step checks VSS sensor for a battery positive supply.
2. 7 - This step checks VSS sensor for a ground supply.
3. 8 - This step checks for a shorted to ground speedometer vehicle speed input circuit.
4. 9 - This step checks VSS for an output signal.
5. 10 - This step checks PCM vehicle speed input circuit for continuity to speedometer.
6. 11 - This step checks speedometer for an output signal. Each one Hz of frequency is approximately equal to one mile per hour.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 6 - This step simulates Pulse Width Modulated (PWM) signal supplied to IAC valve by PCM by rapidly grounding and un-grounding terminal No. 1 of IAC valve.
2. 8 - The most likely cause of no power is an open circuit condition between IAC valve connector terminal No. 2 and splice. A shorted or inoperative EFI relay circuit will cause a no-start condition.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 1 - The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store freeze frame data on scan tool if applicable. This creates an electronic copy of data taken when fault occurred. Information is then stored in scan tool for later reference.
2. 2 - This step checks whether a DTC P1600 is result of a hard failure or an intermittent condition.
3. 3 - This step checks for battery positive voltage at electrical connector of the underhood fuse block. If EFI fuse was faulty, or if there was no voltage to the fuse, vehicle would not start and there would be no MIL or serial data communication.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 3 - This step attempts to repeat the condition that set the DTC.
2. 6 - This step tests the circuit for an open or high resistance.
3. 7 - This step tests the circuit for a short to ground.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 1 - The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store freeze frame data, if applicable. This creates an electronic copy of data taken when fault occurred. Information is then stored in the scan tool for later reference.
2. 2 - If DTCs P1300, P1305, P1310, and P1315 are present, fault is located in the shared electrical circuits or shared components of the ignition coils.
3. 3 - If there is no engine misfire present, there is a fault in Ignition Fail-Safe Input signal circuit.
4. 4 - DTC P1300 indicates a failure in the circuits of ignition coil 1. DTC P1305 indicates a fault with ignition coil 2. DTC P1310 indicates a fault with ignition coil 3. DTC P1315 indicates a fault with ignition coil 4.
5. 5 - This step tests for an open or a short in the ignition trigger signal circuit. Voltage on the ignition trigger signal circuit will fluctuate very quickly when starting or running the engine. DMM voltage reading on the ignition trigger signal circuit should indicate 0.2-1.0 volt. Using min/max feature on DMM may indicate a maximum voltage as high as 3.5 volts.
6. 11 - This step tests for a fault in the Ignition Fail-Safe input circuit. If the cause of DTCs P1300, P1305, P1310, and P1315 is a fault in the ignition fail-safe input circuit, the engine will start and run for less than 2 seconds. Without fail-safe signal, PCM will initiate fuel cutoff.
7. 13 - This step tests for a short in the ignition positive voltage supply to the ignition coils or for a faulty noise filter. A shorted noise filter may pull down ignition coil primary voltage.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 1 - The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store freeze frame data, if applicable. This creates an electronic copy of data taken when fault occurred. The information is then stored in the scan tool for later reference.
2. 2 - This step checks whether DTC P1335 is the result of a hard failure or an intermittent condition. If engine will not start, crank engine over for 3 consecutive ignition cycles.
3. 3 - This step is checking the internal resistance of the CKP sensor and tests if CKP sensors windings are opened or shorted.
4. 4 - Using a DMM, measure resistance of wires between PCM connector to CKP connector. If DMM reads higher than 0.5 ohms, check for a short or high resistance in the circuit. Also, using a test light connected to ground with both PCM and CKP connectors unplugged, probe each connector terminal. This will determine if there is a short to battery voltage.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 1 - The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store freeze frame data, if applicable. This creates an electronic copy of data taken when fault occurred. Information is then stored in scan tool for later reference.
2. 3 - This step checks operation of CMP actuator system. When commanded ON, CMP actuator solenoid advances the camshaft, usually causing engine to stall.
3. 4 - This step visually inspects operation of CMP actuator solenoid valve. Solenoid plunger and spool valve movement should be smooth and rapid from extended to retracted.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 1 - The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store freeze frame data, if applicable. This creates an electronic copy of data taken when fault occurred. Information is then stored in scan tool for later reference.
2. 3 - This step checks operation of CMP actuator system. When commanded ON, CMP actuator solenoid advances camshaft, usually causing engine to stall.
3. 4 - This step visually inspects operation of CMP actuator solenoid valve. Solenoid plunger and spool valve movement should be smooth and rapid from extended to retracted.
4. 7 - This step checks for electrical resistance in wiring and connections of CMP actuator solenoid circuit. Circuit resistance as small as 15 ohms can cause solenoid to malfunction and DTC P1349 to set.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 1 - The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store freeze frame data on, if applicable. This creates an electronic copy of data taken when fault occurred. Information is then stored in scan tool for later reference.
2. 4 - This step checks operation of CMP actuator solenoid valve. This inspection is to be performed when vehicle is idling at normal operating temperature. Turning ON CMP actuator solenoid at idle will advance camshaft enough to cause a significant drop in engine speed.
3. 8 - This step checks for electrical resistance in wiring and connections of CMP actuator solenoid circuit. Circuit resistance as small as 25 ohms can cause a DTC P1656 to set.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 1 - The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store freeze frame data, if applicable. This creates an electronic copy of data taken when fault occurred. Information is then stored in scan tool for later reference.
2. 4 - This step checks the operation of rocker arm oil control solenoid. This inspection is to be performed when vehicle is at normal operating temperature with engine speed at 1500-2500 RPM. Turning ON the rocker arm oil control solenoid will increase valve lift enough to cause a significant drop in engine speed.
3. 8 - This step checks for electrical resistance in wiring and connections of rocker arm oil control solenoid circuit. Circuit resistance as small as 45 ohms can cause a DTC P1690 to set.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 1 - The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store freeze frame data, if applicable. This creates an electronic copy of data taken when fault occurred. Information is then stored in the scan tool for later reference.
2. 2 - This step checks whether rocker arm oil control solenoid is stuck ON. When ON at idle or low engine speed, the solenoid increases valve lift enough to cause engine to run rough or stall.
3. 7 - Rocker arm oil pressure switch is closed when oil pressure is less than 3 psi (20 kPa).
4. 9 - This step visually inspects operation of rocker arm oil control solenoid. Solenoid plunger and spool valve movement should be smooth and rapid from extended to retracted positions.

The numbers below refer to the step numbers in the diagnostic procedures.

1. 1 - The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store the FREEZE FRAME data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
2. 3 - This step checks the operation of the rocker arm oil control solenoid. When commanded ON, the rocker arm oil control solenoid increases valve lift enough to cause the engine to run rough or to stall.
3. 4 - This step visually inspects the operation of the rocker arm oil control solenoid. The solenoid plunger and spool valve movement should be smooth and rapid from extended to retracted.
4. 8 - This step tests the operation of the rocker arm oil pressure switch. The oil pressure switch is normally closed to ground with less than 3 psi (20.7 kPa) of oil pressure. With the oil control solenoid energized oil pressure will open the switch and the test light should turn off momentarily before the engine stalls.
5. 11 - This step checks for electrical resistance in the wiring and connections of the rocker arm oil control solenoid circuit. Circuit resistance as small as 25 ohms can cause the solenoid to malfunction and a DTC P1693 to set.