P 0492 H C Code
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Cruising
Joined: Jan 2008
Posts: 11
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From: Houston Texas
P 0492 H C Code
On my 04 I installed a Vararam back in January, and now I am getting a P 0492 code. At first it would happen when the outside temperature was in the 30's but today it happened on the way home from work at an outside temperature of 79 degrees. Any help would be appreciated.
Safety Car
Joined: Jan 2001
Posts: 4,385
Likes: 689
From: Boise ID
DTC P0491 or P0492
Circuit Description
The secondary air injection (AIR) pump system is designed to lower exhaust emission levels on a start up. The AIR pump is timed to remain ON for approximately 1 minute or until Closed Loop is achieved.
The powertrain control module (PCM) commands the AIR pump relay ON by supplying a ground to the AIR pump relay control circuit. This action energizes the AIR pump, forcing fresh air into the exhaust stream. The PCM also commands the AIR solenoid ON which applies engine vacuum to the AIR shut-off valve. With vacuum applied to the AIR shut-off valve, airflow from the AIR pump flows through the pipes/hoses to the exhaust check valves, then enters into the exhaust stream. The air, oxygen, that is introduced into the exhaust system accelerates catalyst operation. When inactive, the check exhaust valves and the shut-off valve prevent air flow in either direction.
The PCM detects a system air flow condition by monitoring the heated oxygen sensors (HO2S) and Short Term Fuel Trim during normal Open Loop AIR system operation. This is a passive test. If the passive test indicates a pass, the PCM takes no further action. If the passive test fails or is inconclusive, the diagnostic will proceed with an intrusive or active test. The PCM will command the AIR system ON during Closed Loop operation under normal operating conditions. The active test will pass or fail based on the response from the HO2S. A lean HO2S response indicates that the AIR system is functioning normally. An increasing Short Term Fuel Trim value also indicates a normal functioning system. The AIR diagnostic consists of the passive test and the active tests. The AIR diagnostic requires failure of the passive and active tests on 2 consecutive key cycles to illuminate the malfunction indicator lamp (MIL) and stores a DTC. If the PCM detects that the HO2S and Short Term Fuel Trim did not respond as expected on one of the engine banks, DTC P0491 for bank 1 or DTC P0492 for bank 2 sets.
Conditions for Running the DTC
DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0125, P0131, P0132, P0133, P0134, P0135, P0136, P0137, P0138, P0140, P0151, P0154, P0155, P0156, P0157, P0158, P0160, P0161, P0171, P0172, P0174, P0175, P0200, P0220, P0300, P0335, P0336, P0351, P0352, P0353, P0354, P0355, P0356, P0357, P0358, P0442, P0443, P0446, P0449, P0455, P0496, P1133, P1134, P1153, P1154, P1258, P2135 are not set.
The mass air flow (MAF) is less than 23 g/s.
The air/fuel ratio is 14.7:1.
The engine load is less than 40 percent.
The ignition voltage is more than 11.7 volts.
The engine speed is more than 850 RPM.
The engine coolant temperature (ECT) is between -10 and +110°C (14-230°F) .
The intake air temperature (IAT) is between -10 and +100°C (14-212°F) .
The fuel system is operating in fuel trim cells 1, 2, 4, 5, or 6.
The engine is not operating in the following Modes:
Power Enrichment
Decel Fuel Shut-off
Catalyst Over-Temperature
Conditions for Setting the DTC
The HO2S voltage does not decrease to less than 222 mV for 1.3 seconds. AND
The short-term fuel trim does not change more than a predetermined value.
Action Taken When the DTC Sets
The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
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
The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.
Conditions for Setting the DTC
The HO2S voltage does not decrease to less than 222 mV for 1.3 seconds. OR
The short-term fuel trim does not change more than a predetermined value.
Circuit Description
The secondary air injection (AIR) pump system is designed to lower exhaust emission levels on a start up. The AIR pump is timed to remain ON for approximately 1 minute or until Closed Loop is achieved.
The powertrain control module (PCM) commands the AIR pump relay ON by supplying a ground to the AIR pump relay control circuit. This action energizes the AIR pump, forcing fresh air into the exhaust stream. The PCM also commands the AIR solenoid ON which applies engine vacuum to the AIR shut-off valve. With vacuum applied to the AIR shut-off valve, airflow from the AIR pump flows through the pipes/hoses to the exhaust check valves, then enters into the exhaust stream. The air, oxygen, that is introduced into the exhaust system accelerates catalyst operation. When inactive, the check exhaust valves and the shut-off valve prevent air flow in either direction.
The PCM detects a system air flow condition by monitoring the heated oxygen sensors (HO2S) and Short Term Fuel Trim during normal Open Loop AIR system operation. This is a passive test. If the passive test indicates a pass, the PCM takes no further action. If the passive test fails or is inconclusive, the diagnostic will proceed with an intrusive or active test. The PCM will command the AIR system ON during Closed Loop operation under normal operating conditions. The active test will pass or fail based on the response from the HO2S. A lean HO2S response indicates that the AIR system is functioning normally. An increasing Short Term Fuel Trim value also indicates a normal functioning system. The AIR diagnostic consists of the passive test and the active tests. The AIR diagnostic requires failure of the passive and active tests on 2 consecutive key cycles to illuminate the malfunction indicator lamp (MIL) and stores a DTC. If the PCM detects that the HO2S and Short Term Fuel Trim did not respond as expected on one of the engine banks, DTC P0491 for bank 1 or DTC P0492 for bank 2 sets.
Conditions for Running the DTC
DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0125, P0131, P0132, P0133, P0134, P0135, P0136, P0137, P0138, P0140, P0151, P0154, P0155, P0156, P0157, P0158, P0160, P0161, P0171, P0172, P0174, P0175, P0200, P0220, P0300, P0335, P0336, P0351, P0352, P0353, P0354, P0355, P0356, P0357, P0358, P0442, P0443, P0446, P0449, P0455, P0496, P1133, P1134, P1153, P1154, P1258, P2135 are not set.
The mass air flow (MAF) is less than 23 g/s.
The air/fuel ratio is 14.7:1.
The engine load is less than 40 percent.
The ignition voltage is more than 11.7 volts.
The engine speed is more than 850 RPM.
The engine coolant temperature (ECT) is between -10 and +110°C (14-230°F) .
The intake air temperature (IAT) is between -10 and +100°C (14-212°F) .
The fuel system is operating in fuel trim cells 1, 2, 4, 5, or 6.
The engine is not operating in the following Modes:
Power Enrichment
Decel Fuel Shut-off
Catalyst Over-Temperature
Conditions for Setting the DTC
The HO2S voltage does not decrease to less than 222 mV for 1.3 seconds. AND
The short-term fuel trim does not change more than a predetermined value.
Action Taken When the DTC Sets
The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
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
The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.
Conditions for Setting the DTC
The HO2S voltage does not decrease to less than 222 mV for 1.3 seconds. OR
The short-term fuel trim does not change more than a predetermined value.
