Engine Control System - 3.6l (ly7) (DTC p0420 to DTC p1551) Cadillac STS I

Circuit Description

In order to maintain a reasonably low emission level of hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx) a 3-way catalytic converter (TWC) is used. The catalyst within the converter promotes a chemical reaction that oxidizes the HC and CO present in the exhaust gas. This reaction converts the gases into harmless water vapor and carbon dioxide. The catalyst also reduces the NOx, converting the NOx into nitrogen. The engine control module (ECM) monitors this process using the post catalyst heated oxygen sensor (HO2S) signal. The post-catalyst HO2S located in the exhaust stream after the TWC, produces an output signal that indicates the oxygen storage capacity of the catalyst. The oxygen storage capacity (OSC) determines the ability of the catalyst to convert the exhaust emissions effectively. If the catalyst is functioning correctly, the post-catalyst HO2S signal will be far less active than the signal produced by the pre-catalyst HO2S.

To determine OSC, the ECM commands a rich air/fuel mixture until all oxygen is removed from the catalyst. The ECM then commands a lean air/fuel mixture and monitors the rear heated oxygen sensors to calculate the oxygen storage capacity. The catalyst is operated in this mode until one of the following conditions occur

1. The oxygen stored in the catalyst exceeds a calibrated threshold, which is determined from the rear HO2S signal.
2. The rear HO2S indicates the catalyst to be completely saturated with oxygen, which is determined from the rear HO2S signal.

If the ECM detects the average OSC is less than a threshold, this DTC sets. This indicates that the TWC oxygen storage capacity is below a threshold considered acceptable.

DTC Descriptors

This diagnostic procedure supports the following DTCs

1. DTC P0420 Catalyst System Low Efficiency Bank 1
2. DTC P0430 Catalyst System Low Efficiency Bank 2

Conditions for Running the DTC

1. Before the ECM can report DTC P0420 or P0430 failed, DTCs P0030, P0031, P0032, P0036, P0037, P0038, P0050, P0051, P0052, P0053, P0056, P0057, P0058, P0059, P0101, P0102, P0103, P0121, P0122, P0123, P0130, P0131, P0132, P0133, P0135, P0137, P0138, P0140, P0141, P0150, P0151, P0152, P0153, P0155, P0157, P0158, P0160, P0161, P0221, P0222, P0223, P0335, P0336, P0338, P167A, P167B, P2096, P2097, P2098, P2099, P2195, P2196, P2197, P2198, P2232, P2235, P2237, P2240, P2243, P2247, P2251, P2254, P2270, P2271, P2272, P2273, P2297, P2298, P2626, and P2629 must run and pass.
2. DTCs P0010, P0011, P0013, P0014, P0020, P0021, P0023, P0024, P0030, P0031, P0032, P0036, P0037, P0038, P0050, P0051, P0052, P0053, P0056, P0057, P0058, P0059, P0101, P0102, P0103, P0117, P0118, P0121, P0122, P0123, P0125, P0130, P0131, P0132, P0133, P0135, P0137, P0138, P0140, P0141, P0150, P0151, P0152, P0153, P0155, P0157, P0158, P0160, P0161, P0221, P0222, P0223, P0300, P0301-P0306, P0443, P0458, P0459, P0496, P167A, P167B, P2088, P2089, P2090, P2091, P2092, P2093, P2094, P2095, P2096, P2097, P2098, P2099, P2100, P2101, P2107, P2119, P2122, P2123, P2127, P2128, P2138, P2176, P2177, P2178, P2179, P2180, P2187, P2188, P2189, P2190, P2195, P2196, P2197, P2198, P2232, P2235, P2237, P2240, P2243, P2247, P2251, P2254, P2270, P2271, P2272, P2273, P2297, P2298, P2626, and P2629 are not set.
3. The air flow into the engine is between 5.0-16.0 g/s and not changing more than 3.0 g/s
4. The engine coolant temperature (ECT) at engine start-up is more than -30°C (-22°F).
5. The engine is operating for more than 5 minutes.
6. The engine is operating in Closed Loop.
7. The calculated TWC temperature is between 500-750°C (932-1,382°F) and steady.
8. The above conditions exist for approximately 17 minutes.
9. DTCs P0420 and P0430 run once a drive cycle. The ECM will attempt to run this diagnostic up to 4 times a drive cycle.

Conditions for Setting the DTC

The ECM determines that the catalyst efficiency has degraded below a calibrated threshold for more than 4 seconds.

Action Taken When the DTC Sets

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

P0420 or P0430 Catalyst System Low Efficiency Bank 1 or 2

System Description

This diagnostic tests the evaporative emission (EVAP) system for a small leak. The diagnostic runs when the ignition is in the OFF position, and the correct conditions are met. While the engine is operating, there are sources of heat transferred into the fuel tank from the following

1. Exhaust heat
2. Engine heat
3. Ambient temperature

When the engine is stopped and the ignition is in the OFF position, a change in the fuel tank vapor temperature occurs. This results in a change in the pressure of the fuel tank vapor space. This change in pressure is monitored by the control module, using the fuel tank pressure (FTP) sensor input. The EVAP diagnostic detects leaks as small as 0.51 mm (0.02 in). If the control module detects a change in the fuel tank vacuum/pressure less than a calibrated amount, this DTC sets.

DTC Descriptor

This diagnostic procedure supports the following DTC

DTC P0442 Evaporative Emission (EVAP) System Small Leak Detected

1. DTCs P0101, P0102, P0103, P0112, P0113, P0117, P0118, P0125, P0128, P0443, P0446, P0449, P0451, P0452, P0453, P0458, P0459, P0496, P0498, P0499, P0560, P0562, P0721, P0722, P0563, P0721, P0722, P2228, and P2229 are not set.
2. The ignition 1 voltage is more than 10.8 volts.
3. A refueling event is not detected.
4. The fuel volatility is not excessive.
5. The ambient air temperature (AAT) is between 2-32°C (35-90°F).
6. The intake air temperature (IAT) is between 2-32°C (35-90°F) at start-up.
7. The engine coolant temperature (ECT) is less than 42°C (108°F) at start-up.
8. The ECT and the IAT are within 10°C (18°F) of each other at engine start-up.
9. The barometric pressure (BARO) is more than 68 kPa.
10. The engine coolant temperature (ECT) during the previous ignition was more than 74°C (165°F).
11. The fuel level is between 12-88 percent.
12. The vehicle traveled more than 8 km (5 mi) with vehicle speed above 2.5 km/h (1.6 mph).
13. The engine run time is more than 10 minutes.
14. DTC P0442 runs once per engine off cycle when the above conditions have been met prior to engine shut down.

The control module detects approximately 8 vacuum/pressure changes significantly less than a calibrated amount.

1. The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

1. The control module turns OFF the MIL after approximately 6 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

Diagnostic Aids

1. To help locate an intermittent leak, use the J 41413-200 Evaporative Emission System Tester (EEST) to introduce smoke into the EVAP system. See «Special Tools»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction__special-tools) . Move all EVAP components while observing smoke with the J 41413-SPT High Intensity White Light. See «Special Tools»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction__special-tools) . Introducing smoke in 15-second intervals will allow less pressure into the EVAP system. When the system is less pressurized, the smoke will sometimes escape in a more condensed manner.
2. To improve the visibility of the smoke exiting the EVAP system, observe the suspected leak area from different angles with the J 41413-SPT . See «Special Tools»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction__special-tools) .
3. For an intermittent condition, refer to «Intermittent Conditions»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

Test Description

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

1. 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.
2. 5: This step verifies that repairs are complete and that no other condition is present.

DTC P0442

The evaporative emission (EVAP) canister purge valve is used to purge fuel vapor from the EVAP canister to the intake manifold. The EVAP canister purge valve is pulse width modulated (PWM). Ignition voltage is supplied directly to the EVAP canister purge valve. The engine control module (ECM) controls the solenoid by grounding the control circuit with a solid state device called a driver. The driver is equipped with a feedback circuit that is pulled-up to a voltage. The ECM can determine if the control circuit is open, shorted to ground, or shorted to a voltage by monitoring the feedback voltage. If the ECM detects the control circuit voltage is within a predetermined range when the circuit is commanded OFF, this DTC sets.

This diagnostic procedure supports the following DTC

DTC P0443 Evaporative Emission (EVAP) Purge Solenoid Control Circuit

1. The engine speed is more than 80 RPM.
2. The ignition 1 voltage is between 10.5-18 volts.
3. The ECM has commanded the EVAP canister purge valve ON and OFF at least once during the ignition cycle.
4. DTC P0443 runs continuously once the above conditions have been met.

1. The ECM detects the voltage on the EVAP canister purge valve control circuit is between 2.6-4.6 volts when the driver is commanded OFF.
2. The condition exists for less than 4 second.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
2. The lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to «Engine Controls Component Views»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction) .
3. If the condition is intermittent, move the related harnesses and connectors, with the engine operating, while monitoring the circuit status for the component with a scan tool. The circuit status parameter changes from OK or Indeterminate to Fault if there is a condition with the circuit or a connection. The ODM information is in the output driver module (ODM) data list.
4. For an intermittent condition, refer to «Intermittent Conditions»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

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

1. 2: This step determines if the condition exists.
2. 4: This step tests the control modules ability to supply a ground to the EVAP canister purge valve.
3. 5: This step tests the feedback voltage from the ECM. If a voltage is not available, this indicates an internal ECM condition.
4. 6: This step tests the ignition 1 voltage circuit to the EVAP canister purge valve.

DTC P0443 Evaporative Emission (EVAP) Purge Solenoid Control Circuit

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 Open and the EVAP canister vent solenoid 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 Closed and the EVAP canister vent solenoid 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 valves.

DTC P0446

This diagnostic procedure supports the following DTC

DTC P0446 Evaporative Emission (EVAP) Vent System Performance

1. Before the ECM can report DTC P0446 failed, DTCs P0451, P0452, and P0453 must run and pass.
2. DTCs P0101, P0102, P0103, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0221, P0222, P0223, P0443, P0449, P0458, P0459, P0496, P0498, P0499, P0560, P0562, P0563, P0722, P0723, P2122, P2123, P2127, P2128 and P2138 are not set.
3. The ignition 1 voltage is more than 10.5 volts.
4. The fuel system is operating in Closed Loop.
5. The engine run time is more than 10 minutes or the fuel trim is stable.
6. The engine is idling.
7. The fuel tank pressure (FTP) is between -10.0 and 4.0 in. H2O (-18.7 and 7.5 mm Hg).
8. The ambient air temperature (AAT) is between 2-32°C (35-90°F).
9. The ECT and the ambient air temperature (AAT) are within 10°C (18°F) of each other at engine start-up.
10. The fuel level is between 12-88 percent.
11. The vehicle speed sensor (VSS) is less than 2 km/h (3 mph).
12. The above conditions exist for more than 5 seconds.
13. DTC P0446 will attempt to run up to 10 times or the test completes successfully once per ignition cycle.

1. The FTP is less than -3.2 in. H2O (-6.0 mm Hg).
2. The condition is present for more than 4 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

An intermittent condition could be caused by a damaged EVAP vent housing, a temporary blockage at the EVAP vent valve inlet, or a pinched vent hose. A blockage in the vent system will also cause a poor fuel fill condition.

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

1. 3: This step determines if a condition exists with the fuel tank pressure (FTP) sensor. The FTP sensor parameter should display near zero inches of H2O with the fuel fill cap removed and the EVAP purge hose disconnected from the EVAP purge solenoid. Higher ambient air temperatures, or vehicle under-body temperatures could cause a higher than normal FTP reading. Allow the vehicle and/or the air surrounding the fuel tank to cool before proceeding with this step.

1. 4: The EVAP vent solenoid valve is located inside the EVAP canister. The EVAP canister must be removed from the vehicle to access the EVAP vent solenoid valve. Once the EVAP solenoid vent valve has been removed from the EVAP canister, the electrical connector is re-connected. The vent solenoid valve is observed while being commanded ON and OFF with a scan tool.

DTC P0446

The evaporative emission (EVAP) canister vent valve is used for EVAP system diagnostics. The EVAP canister vent valve is a normally open valve. Battery positive voltage is supplied directly to the EVAP canister vent valve. The engine control module (ECM) controls the solenoid by grounding the control circuit with a solid state device called a driver. The driver is equipped with a feedback circuit that is pulled-up to a voltage. The ECM can determine if the control circuit is open, shorted to ground, or shorted to a voltage by monitoring the feedback voltage. If the ECM detects the control circuit voltage is within a predetermined range when the circuit is commanded OFF, 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 vent valve.

DTC P0449

This diagnostic procedure supports the following DTC

DTC P0449 Evaporative Emission (EVAP) Vent Solenoid Control Circuit

1. Before the ECM can report DTC P0449 failed, DTC P0451 must run and pass.
2. The engine speed is more than 80 RPM.
3. The ignition 1 voltage is between 10.5-18 volts.
4. The ECM has commanded the EVAP canister vent valve ON and OFF at least once during the ignition cycle.
5. DTC P0449 runs continuously once the above conditions have been met.

1. The ECM detects the voltage on the EVAP canister vent valve control circuit is between 2.6-4.6 volts when the driver is commanded OFF.
2. The condition exists for less than 4 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
2. The lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to «Engine Controls Component Views»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction) .
3. If the condition is intermittent, move the related harnesses and connectors, with the engine operating, while monitoring the circuit status for the component with a scan tool. The circuit status parameter changes from OK or Indeterminate to Fault if there is a condition with the circuit or a connection. The ODM information is in the output driver module (ODM) data list.
4. For an intermittent condition, refer to «Intermittent Conditions»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

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

1. 2: This step determines if the condition exists.
2. 4: This step tests the battery positive voltage circuit to the EVAP canister vent valve.
3. 5: This step tests the control modules ability to supply a ground to the EVAP canister vent valve.

DTC P0449 Evaporative Emission (EVAP) Vent Solenoid Control Circuit

The control module monitors the fuel tank pressure (FTP) sensor signal in order to detect vacuum decay and excess vacuum during the evaporative emission (EVAP) diagnostic test. The control module supplies a 5-volt reference and a low reference circuit to the FTP sensor. This DTC sets if the engine control module (ECM) detects one of the following conditions

1. The FTP sensor signal voltage is not within a calibrated range on a cold start-up.
2. The FTP sensor signal does not change by a calibrated amount when purge is active.
3. The FTP sensor signal oscillates more than a calibrated amount when vehicle speed is less than 30 km/h (50 mph).

The following table illustrates the relationship between the FTP sensor signal voltage and the EVAP system pressure/vacuum.

DTC P0451

This diagnostic procedure supports the following DTC

DTC P0451 Fuel Tank Pressure (FTP) Sensor Performance

1. DTCs P0101, P0102, P0103, P0117, P0118, P0125, P0449, P0498, P0506, P0507, P0721, P0722, P2227, P2228, and P2229 are not set.
2. The fuel level is between 12-88 percent.
3. The start-up engine coolant temperature (ECT) is less than 35°C (95°F).
4. The vehicle speed is less than 30 km/h (19 mph).
5. The ECM is commanding purge.
6. The ratio between ambient pressure and the calculated manifold pressure is less than 0.8.
7. DTC P0451 runs continuously once the above conditions are met for more than 25 seconds.

1. The ECM detects that the FTP on a cold start-up is less than -11.9 in H2O (-22.2 mm Hg) or more than 6.0 in H2O (11.2 mm Hg) for 25 seconds.
2. The ECM does not detect a change in tank vacuum when purge duty cycle is more than 40 percent. The change in vacuum must be less than 0.25 in H2O (0.47 mm Hg) when purge is active. This condition requires 3 failures to set the DTC for 10 seconds each time.
3. The ECM detects that the FTP sensor signal oscillates more than 3.26 in. H20 (6.09 mm Hg) from a zero point for more than 25 seconds. The zero point may vary and the vehicle speed must be less than 31 km/h (19 mph) for this test.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The MIL will turn OFF after 3 consecutive ignition cycles in which the diagnostic runs without a fault.
2. A history DTC will clear after 40 consecutive warm-up cycles without a fault.
3. Clear the DTCs with a scan tool.

1. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
2. The lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to «Engine Controls Component Views»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction) .
3. A blocked or clogged EVAP canister vent may set this DTC.
4. A large leak in the EVAP system could cause this DTC to set.
5. For an intermittent condition, refer to «Intermittent Conditions»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

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

1. 2: This step verifies that the condition is present.
2. 3: A large leak in the evaporative emission (EVAP) system could cause this DTC to set. Inspect the entire EVAP system for damaged, loose, or leaking EVAP pipes, hoses, or components. Refer to «DTC P0455»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-dtc-p0420-to-dtc-p1551) if you suspect a leak.
3. 5: The ECM produces a measurable steady state amperage that provides the 5-volt reference to the FTP sensor. If the amperage on the 5-volt reference circuit is less than 80 mA, test the 5-volt reference circuit for an open or high resistance.
4. 6: This step tests the signal circuit of the FTP sensor.

DTC P0451

The evaporative emission (EVAP) system is used to store fuel vapors in order to reduce the amount of fuel vapors into the atmosphere. The fuel tank pressure (FTP) sensor is only used for EVAP system diagnostics. The FTP sensor is a transducer that varies resistance according to changes in the fuel tank pressure. The engine control module (ECM) monitors the FTP sensor signal in order to detect vacuum decay and excess vacuum during the EVAP system diagnostic test. The ECM supplies a 5-volt reference and a low reference circuit to the FTP sensor. If the ECM detects that the FTP sensor signal voltage is too low, this DTC sets.

The following table illustrates the relationship between FTP sensor signal voltage and the EVAP system pressure/vacuum.

DTC P0452

This diagnostic procedure supports the following DTC

DTC P0452 Fuel Tank Pressure (FTP) Sensor Circuit Low Voltage

1. The engine is operating for more than 3 seconds.
2. DTC P0452 runs continuously once the above condition is met.

1. The ECM detects the FTP sensor signal voltage is less than 0.13 volts.
2. The condition is present for more than 4 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
2. The lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to «Engine Controls Component Views»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction) .
3. For an intermittent condition, refer to «Intermittent Conditions»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

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

1. 4: The ECM produces a measurable steady state amperage that provides the 5-volt reference to the FTP sensor. If the amperage on the 5-volt reference circuit is less than 80 mA, test the 5-volt reference circuit for an open or high resistance.
2. 5: This step tests the signal circuit of the FTP sensor.

DTC P0452

The evaporative emission (EVAP) system is used to store fuel vapors in order to reduce the amount of fuel vapors into the atmosphere. The fuel tank pressure (FTP) sensor is only used for EVAP system diagnostics. The FTP sensor is a transducer that varies resistance according to changes in the fuel tank pressure. The engine control module (ECM) monitors the FTP sensor signal in order to detect vacuum decay and excess vacuum during the EVAP system diagnostic test. The ECM supplies a 5-volt reference and a low reference circuit to the FTP sensor. If the ECM detects that the FTP sensor signal voltage is too high, this DTC sets.

The following table illustrates the relationship between the FTP sensor signal voltage and the EVAP system pressure/vacuum.

DTC P0453

This diagnostic procedure supports the following DTC

DTC P0453 Fuel Tank Pressure (FTP) Sensor Circuit High Voltage

1. The engine is operating for more than 3 seconds.
2. DTC P0453 runs continuously once the above condition is met.

1. The ECM detects the FTP sensor signal voltage is more than 4.6 volts.
2. The condition is present for more than 4 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
2. The lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to «Engine Controls Component Views»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction) .
3. A refueling event may cause this DTC to set.
4. A blocked or clogged EVAP canister may cause this DTC to set.
5. For an intermittent condition, refer to «Intermittent Conditions»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

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

1. 2: This step verifies that the condition is present.
2. 4: This step tests the EVAP atmospheric vent for a restriction. Inspect the vent for a restriction if the FTP voltage drops after removing the fuel fill cap.
3. 7: This step test for high resistance in the low reference circuit of the FTP sensor. The ECM must be completely powered down to obtain an accurate resistance reading. It may take up to 30 minutes for the ECM to power down after the ignition key is removed. Removal of the ECM/TCM fuse allows the ECM to power down completely.
4. 8: This step tests the low reference circuit for a short to voltage. A short to voltage on the low reference circuit will damage the ECM. Repair the short to voltage before replacing the ECM, if the voltage on the low reference circuit is more than the specified value.

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 valve OPEN and the EVAP vent 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 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 increases too slowly, 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 valves.

DTC P0455

This diagnostic procedure supports the following DTC

DTC P0455 Evaporative Emission (EVAP) System Large Leak Detected

1. Before the engine control module (ECM) can report DTC P0455 failed, DTCs P0443, P0451, P0458, and P0459 must run and pass.
2. DTCs P0030, P0031, P0032, P0036, P0037, P0038, P0050, P0051, P0052, P0053, P0056, P0057, P0058, P0059, P0101, P0102, P0103, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0130, P0131, P0132, P0133, P0135, P0137, P0138, P0140, P0141, P0150, P0151, P0152, P0153, P0155, P0157, P0158, P0160, P0161, P0221, P0222, P0223, P0443, P0449, P0451, P0452, P0453, P0458, P0459, P0496, P0498, P0499, P0506, P0507, P0560, P0562, P0563, P0721, P0722, P2122, P2123, P2127, P2128, P2138, P2177, P2178, P2179, P2180, P2187, P2188, P2189, P2190, P2195, P2196, P2197, P2198, P2227, P2228, P2229, P2232, P2235, P2237, P2240, P2243, P2247, P2251, P2254, P2270, P2271, P2272, P2273, P2297, P2298, P2626, and P2629 are not set.
3. The ignition 1 voltage is between 10.5-18 volts.
4. The engine run time is more than 10 minutes or the fuel trim is stable.
5. The fuel tank pressure is between -10.0 and +4.0 in. H2O (-18.7 and 7.49 mm Hg).
6. The fuel system is operating in Closed Loop.
7. The engine is idling.
8. The volumetric efficiency is less than 35 percent.
9. The barometric pressure (BARO) is more than 68 kPa.
10. The fuel level is between 12-88 percent.
11. The engine coolant temperature (ECT) is between 4-65°C (39-149°F).
12. The intake air temperature (IAT) is between 4-30°C (39-86°F).
13. The vehicle speed sensor (VSS) is less than 3 km/h (2 mph).
14. The above conditions are met for more than 11 seconds.
15. DTC P0455 will attempt to run up to 10 times or the test completes successfully once per ignition cycle.

1. The ECM detects the EVAP system is not able to achieve or maintain vacuum during the diagnostic test.
2. The condition exists for more than 4 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. To help locate intermittent leaks, use the J 41413-200 Evaporative Emission System Tester (EEST) to introduce smoke into the EVAP system. See «Special Tools»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction__special-tools) . Move all EVAP components while observing smoke with the J 41413-SPT High Intensity White Light. See «Special Tools»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction__special-tools) . Introducing smoke in 15-second intervals will allow less pressure into the EVAP system. When the system is less pressurized, the smoke will sometimes escape in a more condensed manner.
2. A temporary blockage in the EVAP purge solenoid, purge pipe, or EVAP canister could cause an intermittent condition. Inspect and repair any restriction in the EVAP system.
3. A loose, incorrect, missing, or damaged fuel fill cap may cause this DTC to set.
4. To improve the visibility of the smoke exiting the EVAP system, observe the suspected leak area from different angles with the J 41413-SPT . See «Special Tools»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction__special-tools) .
5. Observe the Freeze Frame/Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition occurs that caused the DTC to set. This may assist in diagnosing the condition.
6. For an intermittent condition, refer to «Intermittent Conditions»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

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

1. 4: 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.
2. 6: This step verifies proper operation of the FTP sensor.
3. 7: A normal operating FTP sensor should increase above 5 inches of H2O and stop between 6-7 inches of H2O.
4. 8: This step tests for a obstruction between the fuel tank and the FTP sensor, which is mounted on the EVAP canister, or a failed FTP sensor. Replace the FTP sensor if the pressure on the J 41413-200 gage drops to near 0 inches H2O, with the sensor removed from the canister. See «Special Tools»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction__special-tools) .
5. 10: This step tests the EVAP purge solenoid vacuum source between the EVAP purge solenoid and the intake manifold for restrictions or blockages.

DTC P0455

The evaporative emission (EVAP) canister purge valve is used to purge fuel vapor from the EVAP canister to the intake manifold. The EVAP canister purge valve is pulse width modulated (PWM). Ignition voltage is supplied directly to the EVAP canister purge valve. The engine control module (ECM) controls the solenoid by grounding the control circuit with a solid state device called a driver. The driver is equipped with a feedback circuit that is pulled-up to a voltage. The ECM can determine if the control circuit is open, shorted to ground, or shorted to a voltage by monitoring the feedback voltage. If the ECM detects the control circuit voltage is less than a predetermined value when the circuit is commanded OFF, this DTC sets.

This diagnostic procedure supports the following DTC

DTC P0458 Evaporative Emission (EVAP) Purge Solenoid Control Circuit Low Voltage

1. The engine speed is more than 80 RPM.
2. The ignition 1 voltage is between 10.5-18 volts.
3. The ECM has commanded the EVAP canister purge valve ON and OFF at least once during the ignition cycle.
4. DTC P0458 runs continuously once the above conditions have been met.

1. The ECM detects the voltage on the EVAP canister purge valve control circuit is less than 2.6 volts when the driver is commanded OFF.
2. The condition exists for less than 4 second.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
2. The lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to «Engine Controls Component Views»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction) .
3. If the condition is intermittent, move the related harnesses and connectors, with the engine operating, while monitoring the circuit status for the component with a scan tool. The circuit status parameter changes from OK or Indeterminate to Fault if there is a condition with the circuit or a connection. The ODM information is in the output driver module (ODM) data list.
4. For an intermittent condition, refer to «Intermittent Conditions»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

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

1. 2: This step determines if the condition exists.
2. 5: This step tests the feedback voltage from the ECM. If a voltage is not available, this indicates an internal ECM condition.
3. 6: This step tests the ignition 1 voltage circuit to the EVAP canister purge valve.

DTC P0458 Evaporative Emission (EVAP) Purge Solenoid Control Circuit Low Voltage

The evaporative emission (EVAP) canister purge valve is used to purge fuel vapor from the EVAP canister to the intake manifold. The EVAP canister purge valve is pulse width modulated (PWM). Ignition voltage is supplied directly to the EVAP canister purge valve. The engine control module (ECM) controls the solenoid by grounding the control circuit with a solid state device called a driver. The driver is equipped with a feedback circuit that is pulled-up to a voltage. The ECM can determine if the control circuit is open, shorted to ground, or shorted to a voltage by monitoring the feedback voltage. If the ECM detects the control circuit voltage is more than a predetermined value when the circuit is commanded ON, this DTC sets.

This diagnostic procedure supports the following DTC

DTC P0459 Evaporative Emission (EVAP) Purge Solenoid Control Circuit High Voltage

1. The engine speed is more than 80 RPM.
2. The ignition 1 voltage is between 10.5-18 volts.
3. The ECM has commanded the EVAP canister purge valve ON and OFF at least once during the ignition cycle.
4. DTC P0459 runs continuously once the above conditions have been met.

1. The ECM detects the voltage on the EVAP canister purge valve control circuit is more than 4.6 volts when the driver is commanded ON.
2. The condition is present for more than 4 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
2. The lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to «Engine Controls Component Views»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction) .
3. If the condition is intermittent, move the related harnesses and connectors, with the engine operating, while monitoring the circuit status for the component with a scan tool. The circuit status parameter changes from OK or Indeterminate to Fault if there is a condition with the circuit or a connection. The ODM information is in the output driver module (ODM) data list.
4. For an intermittent condition, refer to «Intermittent Conditions»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

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

1. 2: This step determines if a condition exists. The EVAP canister purge valve is PWM. An audible click should be heard when the purge valve is commanded to 50 percent and should stop when the EVAP canister purge valve is commanded to 0 percent. The rate at which the valve cycles should increase as the commanded state is increased and decreased as the commanded state is decreased. Repeat the commands as necessary.

DTC P0459 Evaporative Emission (EVAP) Purge Solenoid Control Circuit High Voltage

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 valve Closed and the EVAP canister vent 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 valves.

DTC P0496

This diagnostic procedure supports the following DTC

DTC P0496 Evaporative Emission (EVAP) System Flow During Non-Purge

1. Before the engine control module (ECM) can report DTC P0496 failed, DTCs P0451, P0452, and P0453 must run and pass.
2. DTCs P0101, P0102, P0103, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0221, P0222, P0223, P0443, P0446, P0449, P0451, P0452, P0453, P0458, P0459, P0451, P0452, P0453, P0498, P0499, P0560, P0562, P0563, P0722, P0723, P2122, P2123, P2127, P2128, and P2138 are not set.
3. The fuel system is in closed loop.
4. The engine run time is more than 16 minutes or the long term fuel trim is stable.
5. The vehicle speed sensor (VSS) is less than 3 km/h (2 mph).
6. The engine is idling.
7. The ignition 1 voltage is between 10.5-18 volts.
8. The FTP is between -18.7 to +7.5 mm Hg (-10.0 to +4.0 in H2O).
9. The ambient air temperature is between 2-32°C (36-90°F).
10. The start-up engine coolant temperature (ECT) is within 10°C (18°F) of ambient air temperature.
11. The fuel tank level is between 12-88 percent.
12. The volumetric efficiency is less than 35 percent.
13. The barometric pressure (BARO) is more than 68 kPa.
14. The above conditions are met for more than 4 seconds.
15. DTC P0496 will attempt to run up to 10 times or the test completes successfully once per ignition cycle.

1. The control module detects vacuum during a non-purge condition.
2. The condition exists for more than 4 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
2. The lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to «Engine Controls Component Views»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction) .
3. An intermittent condition could be caused by an improperly installed or damaged EVAP canister purge valve or a temporary blockage in the EVAP canister purge valve. For an intermittent condition, refer to «Intermittent Conditions»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions)

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

1. 3: 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.

P0496 Evaporative Emission (EVAP) System Flow During Non-Purge

The evaporative emission (EVAP) canister vent valve is used for EVAP system diagnostics. The EVAP canister vent valve is a normally open valve. Battery positive voltage is supplied directly to the EVAP canister vent valve. The engine control module (ECM) controls the solenoid by grounding the control circuit with a solid state device called a driver. The driver is equipped with a feedback circuit that is pulled up to a voltage. The ECM can determine if the control circuit is open, shorted to ground, or shorted to a voltage by monitoring the feedback voltage. If the ECM detects the control circuit voltage is less than a predetermined value when the circuit is commanded OFF, 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 vent valve.

DTC P0498

This diagnostic procedure supports the following DTC

DTC P0498 Evaporative Emission (EVAP) Vent Solenoid Control Circuit Low Voltage

1. Before the ECM can report DTC P0498 failed, DTC P0451 must run and pass.
2. The engine speed is more than 80 RPM.
3. The ignition 1 voltage is between 10.5-18 volts.
4. The ECM has commanded the EVAP canister vent valve ON and OFF at least once during the ignition cycle.
5. DTC P0498 runs continuously once the above conditions have been met.

1. The ECM detects the voltage on the EVAP canister vent valve control circuit is less than 2.6 volts when the driver is commanded OFF.
2. The condition is present for more than 4 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
2. The lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to «Engine Controls Component Views»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction) .
3. If the condition is intermittent, move the related harnesses and connectors, with the engine operating, while monitoring the circuit status for the component with a scan tool. The circuit status parameter changes from OK or Indeterminate to Fault if there is a condition with the circuit or a connection. The ODM information is in the output driver module (ODM) data list.
4. For an intermittent condition, refer to «Intermittent Conditions»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

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

1. 2: This step determines if a condition exists.
2. 4: This step tests the battery positive voltage circuit to the EVAP canister vent valve.

DTC P0498 Evaporative Emission (EVAP) Vent Solenoid Control Circuit Low Voltage

The evaporative emission (EVAP) canister vent valve is used for EVAP system diagnostics. The EVAP canister vent valve is a normally open valve. Battery positive voltage is supplied directly to the EVAP canister vent valve. The engine control module (ECM) controls the solenoid by grounding the control circuit with a solid state device called a driver. The driver is equipped with a feedback circuit that is pulled-up to a voltage. The ECM can determine if the control circuit is open, shorted to ground, or shorted to a voltage by monitoring the feedback voltage. If the ECM detects the control circuit voltage is more than a predetermined value when the circuit is commanded ON, 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 vent valve.

DTC P0499

This diagnostic procedure supports the following DTC

DTC P0499 Evaporative Emission (EVAP) Vent Solenoid Control Circuit High Voltage

1. Before the ECM can report DTC P0499 failed, DTC P0451 must run and pass.
2. DTC P0455 must run before the ECM enables the EVAP canister vent valve.
3. The engine speed is more than 80 RPM.
4. The ignition 1 voltage is between 10.5-18 volts.
5. The ECM has commanded the EVAP canister vent valve ON and OFF at least once during the ignition cycle.
6. DTC P0499 runs continuously once the above conditions have been met.

1. The ECM detects the voltage on the EVAP canister vent valve control circuit is more than 4.6 volts when the driver is commanded ON.
2. The condition is present for more than 4 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
2. The lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to «Engine Controls Component Views»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction) .
3. If the condition is intermittent, move the related harnesses and connectors, with the engine operating, while monitoring the circuit status for the component with a scan tool. The circuit status parameter changes from OK or Indeterminate to Fault if there is a condition with the circuit or a connection. The output driver module (ODM) information is in the ODM data list.
4. For an intermittent condition, refer to «Intermittent Conditions»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

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

1. 2: This step determines if a condition exists. An audible click should be heard when the EVAP canister vent valve is commanded ON and OFF. Repeat the commands as necessary.

DTC P0499

The throttle actuator control (TAC) motor is a DC motor that is part of the throttle body assembly. The TAC motor drives the throttle valve. The engine control module (ECM) controls the TAC motor based on throttle position sensor input. The idle speed is controlled by the ECM based on various inputs. The ECM commands the TAC motor to open or close the throttle valve in order to maintain the desired idle speed. If the ECM detects the actual idle speed and the desired idle speed are not within a predetermined amount, this DTC sets.

This diagnostic procedure supports the following DTCs

1. DTC P0506 Idle Speed Low
2. DTC P0507 Idle Speed High

1. Before the ECM can report DTC P0506 or P0507 failed, transmission DTCs P0722 and P0723 must run and pass.
2. DTCs P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0221, P0222, P0223, P0442, P0443, P0446, P0455, P0458, P0459, P0496, P0722, and P0723 are not set.
3. The engine coolant temperature (ECT) is more than 60°C (140°F).
4. The intake air temperature (IAT) is more than -10.5°C (+13°F).
5. The volumetric efficiency is less than 35 percent, DTC P0506 only.
6. The evaporative emission (EVAP) canister purge valve is OFF.
7. A vehicle speed was detected prior to the diagnostic running.
8. The vehicle speed is 0 km/h (0 mph).
9. DTC P0506 and P0507 run continuously once the above conditions are met for more than 10 seconds.

Conditions for Setting DTC P0506

The actual engine speed is less than the desired idle speed by at least 100 RPM for 4 seconds.

Conditions for Setting DTC P0507

The actual engine speed is more than the desired idle speed by at least 200 RPM for 4 seconds.

OR

The ECM detects 3 fuel cut-offs due to an engine over speed condition while the engine is idling.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
2. The lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to «Engine Controls Component Views»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction) .
3. For an intermittent condition, refer to «Intermittent Conditions»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

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

1. 2: If any of the listed DTCs are present, correct the condition before returning to this table.
2. 3: This test determines whether the engine can achieve the commanded RPM, and if not, whether the engine speed is too high or too low.

DTC P0506 or P0507

This diagnostic applies to internal microprocessor integrity conditions within the engine control module (ECM). This diagnostic also addresses if the ECM is not programmed.

This diagnostic procedure supports the following DTCs

1. DTC P0601 Control Module Read Only Memory (ROM)
2. DTC P0602 Control Module Not Programmed
3. DTC P0604 Control Module Random Access Memory (RAM)
4. DTC P0606 Control Module Internal Performance

DTC P0601

The checksum calculation at power down in the last drive cycle completely finished. DTC P0601 runs once an ignition cycle.

DTC P0602

The ignition is ON, with the engine OFF. DTC P0602 runs continuously.

DTC P0604

The read/write test at power down in the last drive cycle completely finished. DTC P0604 runs once an ignition cycle.

DTC P0606

DTC P0606 runs continuously with ignition ON or engine operating.

The ECM detects the incorrect read only memory (ROM) checksum for more than 30 seconds.

The ECM detects that programming is incomplete for more than 1 second.

The ECM detects random access memory (RAM) errors for more than 5 seconds.

The ECM detects an internal condition for more than 5 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

For complete details on programming the ECM, refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

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

1. 2: A DTC P0602 indicates the ECM is not programmed.
2. 4: Attempt to program the ECM. If the ECM fails to program a second time, replace the ECM.

DTC P0601, P0602, P0604, P0605, P0606

The engine control module (ECM) provides ignition voltage to the coil side of the fuel pump relay whenever the engine is cranking or running. The control module enables the fuel pump relay as long as the engine is cranking or running, and ignition system reference pulses are received. If no ignition system reference pulses are received, the control module turns OFF the fuel pump.

The fuel pump relay control circuit is equipped with a feedback circuit that is pulled up to 2.5 volts within the ECM. The ECM can determine if the control circuit is open, shorted to ground, or shorted to a voltage by monitoring the feedback voltage. If the ECM detects that the control circuit voltage is within a predetermined range when the circuit is commanded OFF, this DTC sets.

This diagnostic procedure supports the following DTC

DTC P0627 Fuel Pump Relay Control Circuit

1. The engine speed is 0 RPM.
2. The ignition is ON, with the engine OFF.
3. The ignition 1 voltage is more than 10.5 volts.
4. The ECM has commanded the fuel pump relay ON and OFF at least once during the ignition cycle.
5. The above conditions are met for more than 1 second.
6. DTC P0627 runs continuously once the above conditions are met.

1. The ECM detects the voltage on the fuel pump relay control circuit is within predetermined range when the circuit is commanded OFF.
2. The condition exists for less than 4 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
2. The lower connector of the ECM is C1 and the upper connector of the ECM is C2. Refer to «Engine Controls Component Views»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction) .
3. If the condition is intermittent, move the related harnesses and connectors while monitoring the circuit status for the component in the Output Driver Module (ODM) data list with a scan tool. The circuit status parameter changes from OK to Fault if there is a condition with the circuit or a connection.
4. For an intermittent condition, refer to «Intermittent Conditions»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

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

1. 4: This step verifies that the control module is providing voltage to the fuel pump relay.
2. 5: This step tests the ground circuit of the fuel pump relay.

DTC P0627 Fuel Pump Relay Control Circuit Open

The engine control module (ECM) provides ignition voltage to the coil side of the fuel pump relay whenever the engine is cranking or running. The control module enables the fuel pump relay as long as the engine is cranking or running, and ignition system reference pulses are received. If no ignition system reference pulses are received, the control module turns OFF the fuel pump.

The fuel pump relay control circuit is equipped with a feedback circuit that is pulled up to 2.5 volts within the ECM. The ECM can determine if the control circuit is open, shorted to ground, or shorted to a voltage by monitoring the feedback voltage. If the ECM detects the control circuit voltage is less than a predetermined voltage when commanded ON, this DTC sets.

This diagnostic procedure supports the following DTC

DTC P0628 Fuel Pump Relay Control Circuit Low Voltage

1. The fuel pump relay is commanded ON.
2. The ignition 1 voltage is more than 10.5 volts.
3. DTC P0628 runs continuously once the above conditions are met.

1. The ECM detects that the fuel pump relay control circuit is shorted to ground.
2. The condition exists for less than 4 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
2. The lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to «Engine Controls Component Views»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction) .
3. If the condition is intermittent, move the related harnesses and connectors while monitoring the circuit status for the component in the Output Driver Module (ODM) data list with a scan tool. The circuit status parameter changes from OK to Fault if there is a condition with the circuit or a connection.
4. For an intermittent condition, refer to «Intermittent Conditions»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

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

1. 4: This step verifies that the control module is providing voltage to the fuel pump relay.

DTC P0628 Fuel Pump Relay Control Circuit Low Voltage

The engine control module (ECM) provides ignition voltage to the coil side of the fuel pump relay whenever the engine is cranking or running. The control module enables the fuel pump relay as long as the engine is cranking or running, and ignition system reference pulses are received. If no ignition system reference pulses are received, the control module turns OFF the fuel pump.

The fuel pump relay control circuit is equipped with a feedback circuit that is pulled up to 2.5 volts within the ECM. The ECM can determine if the control circuit is open, shorted to ground, or shorted to a voltage by monitoring the feedback voltage. If the ECM detects the control circuit voltage is more than a predetermined voltage when the circuit is commanded OFF, this DTC sets.

This diagnostic procedure supports the following DTC

DTC P0629 Fuel Pump Relay Control Circuit High Voltage

1. The engine speed is 0 RPM.
2. The ignition is ON, with the engine OFF.
3. The ignition 1 voltage is more than 10.5 volts.
4. The above conditions are met for more than 1 second.
5. DTC P0629 runs continuously once the above conditions are met.

1. The ECM detects that the fuel pump relay control circuit is shorted to a voltage.
2. The condition exists for less than 4 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
2. The lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to «Engine Controls Component Views»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction) .
3. If the condition is intermittent, move the related harnesses and connectors while monitoring the circuit status for the component in the Output Driver Module (ODM) data list with a scan tool. The circuit status parameter changes from OK to Fault, if there is a condition with the circuit or a connection.
4. For an intermittent condition, refer to «Intermittent Conditions»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

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

1. 4: This step verifies that the control module is providing voltage to the fuel pump relay.
2. 5: This step tests for an open in the ground circuit to the fuel pump relay.

DTC P0629 Fuel Pump Relay Control Circuit High Voltage

The engine control module (ECM) controls the throttle valve by applying a varying voltage to the control circuits of the throttle actuator control (TAC) motor. The ECM monitors the duty cycle that is required to actuate the throttle valve. The ECM monitors the throttle position (TP) sensors 1 and 2 to determine the actual throttle valve position. If the ECM detects that the duty cycle to control the throttle valve to the desired position is more than a predetermined value, this DTC sets.

This diagnostic procedure supports the following DTC

DTC P0638 Throttle Actuator Control (TAC) Command Performance

1. The ignition is ON or the engine is operating.
2. The ignition 1 voltage is more than 7 volts.
3. DTC P0638 runs continuously once the above conditions are met for more than 1 second.

1. The ECM detects that the commanded duty cycle for the range test high is more than 80 percent for more than 0.6 seconds. OR
2. The ECM detects that the commanded duty cycle for the range test low is more than 80 percent for more than 5 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
2. The lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to «Engine Controls Component Views»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction) .
3. Inspect for a condition in which the throttle valve may have been held open. For example, ice may have formed in the throttle bore causing the throttle valve not to close. Observe the Freeze Frame/Failure Records.
4. The throttle valve is spring loaded to a slightly open position. The throttle valve should be open approximately 3-5 percent. This is referred to as the rest position.
5. The throttle valve should not be completely closed or open any more than a specified amount.
6. The throttle valve should move open and to the closed position without binding under the normal spring pressure.
7. The throttle should NOT be free to move open or closed WITHOUT spring pressure.
8. The scan tool has the ability to operate the throttle control system using the TP function located in the TAC System menu. This function operates the throttle valve through the entire range in order to determine if the TAC system operates correctly. Additional DTCs may set using this function.
9. For an intermittent condition, refer to «Intermittent Conditions»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

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

1. 2: This step determines if the condition exists. A TP sensor DTC may cause this DTC to set.
2. 3: Depending on the condition, DTC P0638, P2100, P2101, and/or P2119 may set individually or together.
3. 8: When the ignition is turn ON, the ECM operates the throttle actuator control motor to verify the integrity of the system prior to start-up. This can be seen by the momentary flash of the test lamp as the ignition is turned ON.

P0638 Throttle Actuator Control (TAC) Command Performance

The malfunction indicator lamp (MIL) is located on the instrument panel cluster (IPC). The MIL informs the driver that an emission system fault has occurred and that the engine control system requires service. The engine control module (ECM) monitors the MIL control circuit for conditions that are incorrect for the commanded state of the MIL. For example, a failure condition exists if the ECM detects low voltage when the MIL is commanded OFF, or high voltage when the MIL is commanded ON. If the ECM detects an improper circuit condition on the MIL control circuit, this DTC sets.

This diagnostic procedure supports the following DTC

DTC P0650 Malfunction Indicator Lamp (MIL) Control Circuit

1. The engine speed is more than 80 RPM.
2. The ignition 1 voltage is between 10-18 volts.
3. The ECM has commanded the MIL ON and OFF at least once during the ignition cycle.
4. DTC P0650 runs continuously once the above conditions are met

1. The ECM detects an open, a short to ground, or a short to voltage on the circuit that controls the MIL.
2. The condition exists for at least 4 seconds.

The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
2. The lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to «Engine Controls Component Views»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction) .
3. For an intermittent condition, refer to «Intermittent Conditions»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

DTC P0650

This diagnostic trouble code (DTC) indicates that an emission related transmission DTC set in the transmission control module (TCM). The engine control module (ECM) receives the TCM information over the serial data circuit. The ECM turns ON the malfunction indicator lamp (MIL) when the TCM sends a message over the serial data circuit requesting MIL illumination. The DTC information for the ECM will only display DTC P0700.

This diagnostic procedure supports the following DTC

DTC P0700 Transmission Control Module (TCM) Requested MIL Illumination

DTC P0700 runs continuously.

The ECM receives a serial data message, from the TCM, in order to illuminate the MIL.

1. The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

DTC P0700 Transmission Control Module (TCM) Requested MIL Illumination

The transmission control module (TCM) sends vehicle speed data to the engine control module (ECM). The data is sent to the ECM through a communication network called the GM local area network (LAN). Two circuits are used to communicate LAN data between the ECM and TCM. A fault in the LAN will not cause DTC P0864 to set by itself. If a LAN fault occurs, other DTCs will set in addition to DTC P0864.

If the ECM receives invalid vehicle speed data from the TCM, this DTC sets.

This diagnostic procedure supports the following DTC

DTC P0864 TCM Communication Circuit Performance

1. The ignition is on for more than 3 seconds.
2. The ignition 1 voltage is between 10.5-18 volts.
3. No other LAN errors are present.
4. DTC P0864 runs continuously once the above conditions are met for more than 2.5 seconds.

The ECM receives no valid vehicle speed data from the TCM for more than 4 seconds.

1. The control module stores the DTC information into memory when the diagnostic runs and fails.
2. The malfunction indicator lamp (MIL) will not illuminate.
3. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
4. The driver information center, if equipped, may display a message.

Conditions for Clearing the DTC

1. A current DTC Last Test Failed clears when the diagnostic runs and passes.
2. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
3. Clear the DTC with a scan tool.

DTC P0864

The camshaft position (CMP) actuator system enables the engine control module (ECM) to change the camshaft timing of all 4 camshafts while the engine is operating. The CMP actuator assembly varies the camshaft position in response to directional changes in oil pressure. The CMP actuator solenoid controls the oil pressure that is applied to advance or retard a camshaft.

The CMP actuator assemblies have an outer housing that is driven by the engine timing chain. Inside the CMP assembly is a wheel with fixed vanes that is attached to the camshafts. The CMP actuator assemblies are also equipped with a locking pin. The locking pin prevents movement between the outer housing and the wheel vane assembly on engine start-ups. The CMP actuator is locked until sufficient oil pressure is available to control the CMP actuator. The locking pin is released by oil pressure before any movement in the CMP actuator assembly takes place. If the ECM detects that the CMP actuator is not in the locked position on a start-up, this DTC sets.

This diagnostic procedure supports the following DTCs

1. DTC P1011 Intake Camshaft Position (CMP) Actuator Park Position Bank 1
2. DTC P1012 Exhaust Camshaft Position (CMP) Actuator Park Position Bank 1
3. DTC P1013 Intake Camshaft Position (CMP) Actuator Park Position Bank 2
4. DTC P1014 Exhaust Camshaft Position (CMP) Actuator Park Position Bank 2

1. DTCs P0010, P0013, P0020, P0023, P2088, P2089, P2090, P2091, P2092, P2093, P2094, and P2095 are not set.
2. The engine is operating for more than 1 second.
3. The ECM completed the CMP actuator solenoid output driver test.
4. The engine speed is more than 1,000 RPM.
5. DTC P1011, P1012, P1013, and P1014 only runs on an engine start-up.

The ECM detects that a CMP actuator is not in the parked position on an engine start-up.

1. The control module stores the DTC information into memory when the diagnostic runs and fails.
2. The malfunction indicator lamp (MIL) will not illuminate.
3. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
4. The driver information center, if equipped, may display a message.

1. A current DTC Last Test Failed clears when the diagnostic runs and passes.
2. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
3. Clear the DTC with a scan tool.

1. The following conditions cause DTC P1011, P1012, P1013, and P1014 to set: Turning the engine OFF while the accelerator pedal is pressed Turning the engine OFF while driving Pressing the accelerator pedal to start the engine An engine idle flare during a start-up An actuator that is in the full advance or retard position
2. For an intermittent condition, refer to «Intermittent Conditions»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

DTC P1011-P1014

The engine control module (ECM) controls the throttle valve by applying a varying voltage to the control circuits of the throttle actuator control (TAC) motor. The ECM monitors the duty cycle that is required to actuate the throttle valve. The ECM monitors the throttle position (TP) sensors 1 and 2 to determine the actual throttle valve position. If the ECM detects that the throttle position is NOT within a predetermined range when commanded to the rest position, this DTC sets.

This diagnostic procedure supports the following DTC

DTC P1551 Throttle Valve Rest Position Not Reached During Learn

1. The vehicle speed is 0 km/h (0 mph).
2. The engine speed is less than 40 RPM.
3. The engine coolant temperature (ECT) is 5-85°C (41-185°F).
4. The intake air temperature (IAT) is 5-60°C (41-140°F).
5. The ignition 1 voltage is more than 10 volts.
6. The accelerator pedal position (APP) is less than 15 percent.
7. DTC P1551 runs when the throttle actuator control motor is deactivated.

The ECM detects the TP sensor angle is less than 1.8 percent or more than 13.1 percent for more than 4 seconds, when the throttle actuator control motor is deactivated.

1. The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
2. Operating the throttle valve with the Throttle Position control function of the scan tool may cause additional DTCs to set. DO NOT attempt to diagnose DTCs set during this function.
3. The scan tool has the ability to operate the throttle actuator control system using Special Functions. This function operates the throttle through the entire range in order to determine if the throttle body and system operate correctly.
4. Inspect for a condition in which the throttle valve may have been held open.
5. Inspect for conditions in which ice may have formed in the throttle bore.
6. For an intermittent condition, refer to «Intermittent Conditions»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

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

1. 5: The throttle valve is spring loaded to a slightly open position. The throttle valve should be open approximately 3-5 percent. This is referred to as the rest position. The throttle valve should not be completely closed, nor should they be open any more than the specified amount. The throttle valve should move open and to the closed position without binding under the normal spring pressure. The throttle should NOT be free to move open or closed WITHOUT spring pressure. Replace the throttle body if any of these conditions are found. The throttle valve is spring loaded in a slightly open position and should move in either direction without binding. The throttle valve should always be under spring pressure.

DTC P1551 Throttle Valve Rest Position Not Reached During Learn

See also:
• Engine Controls Schematics
• Engine Control Module (ECM) Connector End Views
• Engine Controls Connector End Views
• Diagnostic System Check - Vehicle
• Diagnostic Trouble Code (DTC) List - Vehicle
• Catalytic Converter Replacement - Left (LY7)
• Special Tools
• Intermittent Conditions
• Lifting and Jacking the Vehicle
• Circuit Testing
• Wiring Repairs
• Testing for Intermittent Conditions and Poor Connections
• Connector Repairs
• Control Module References
• DTC P2105
• DTC P0121
• DTC P0221
• Disengaging Connectors Notice
• Instrument Cluster Schematics
• Data Link Connector (DLC) Schematics
• Automatic Transmission Related Connector End Views (5L40-E)
• Fluid and Lubricant Recommendations
• Oil Pressure Diagnosis and Testing
• Camshaft Position (CMP) Actuator Replacement - Bank 2 (Left) Exhaust
• Symptoms - Engine Controls
• DTC P0455