2001 Chevrolet S10 Q&A
2001 Chevrolet S10 Question: the check engine light keeps coming on
Circuit Description The Secondary Air Injection (AIR) System is designed to lower exhaust emission levels during a cold or warm start. The AIR pump is timed to remain ON for approximately one minute after the engine is started. The powertrain control module (PCM) commands the AIR pump relay ON by supplying a ground on the control circuit. This action energizes the AIR pump, forcing air into the exhaust stream. The PCM also commands the AIR vacuum control solenoid valve ON which applies vacuum to the AIR shut-off valve. When vacuum is applied to the AIR shut-off valve, airflow from the AIR pump flows through the hoses/pipes and to the exhaust check valves. The air then enters into the exhaust stream. The air that is introduced into the exhaust system accelerates catalyst operation by decreasing the time it takes for the convertor to begin its process of burning the incomplete gases; reducing engine exhaust emission levels. When inactive, the check valves and the shut-off valve prevent airflow in either direction. The PCM detects a system airflow problem by monitoring the heated oxygen sensors (HO2S) and short term fuel trim during normal Open Loop AIR system operation. This is called 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 tests. 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 secondary AIR system is functioning normally. An increasing short term fuel trim value also indicates a normally 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 two consecutive key cycles to illuminate the malfunction indicator lamp (MIL) and store a DTC. If the PCM detects that the HO2S and short term FT did not respond as expected on one of the engine banks, DTC P1415 or P1416 sets. If the PCM detects that the HO2S and short term FT did not respond as expected on both of the engine banks, DTC P0410 sets. Conditions for Running the DTC DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0155, P0171, P0172, P0174, P0175, P0300, P0440, P0442, P0446, P0506, or P0507 are not set. The engine run time is more than 15 seconds after Closed Loop operation. The engine load is less than 33 percent. The engine air flow is less than 18 g/s. The engine speed is more than 750 RPM. The ignition voltage is more than 11.7 volts. The engine coolant temperature (ECT) is 70-110°C (158-230°F). The intake air temperature (IAT) is more than 2°C (36°F). The fuel system is not operating in power enrichment or deceleration fuel cut-off (DFCO). The short term fuel trim is between +5 and -5 percent. The startup ECT is below 80°C (176°F). The vehicle speed is more than 25 km/h (15 mph). Conditions for Setting the DTC The HO2S voltage does not decrease to less than 222 mV within 1.2 seconds when the AIR pump turns on during Closed Loop operation. AND Short term fuel trim does not increase above a predetermined amount. 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. Diagnostic Aids Important: Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing or replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the PCM. Using Freeze Frame/Failure Records may aid in locating an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame/Failure Records can aid in determining how many miles the vehicle has been driven since the DTC set. The Fail Counter and Pass Counter can also aid in determining how many ignition cycles the diagnostic reported a pass or a fail. Operate the vehicle within the same Freeze Frame conditions, such as RPM, load, vehicle speed, temperature etc., that you observed. This will isolate when the DTC failed. An intermittent may be caused by any of the following conditions: Low system air flow may cause this DTC to set. Excessive exhaust system back pressure Moisture, water, or debris ingested into the AIR pump Pinched, kinked, heat damaged, or deteriorated hoses or vacuum hoses Restriction in the pump inlet, duct, or filter Thoroughly inspect any circuitry that is suspected of causing the intermittent complaint. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. If a repair is necessary, refer to Wiring Repairs or Connector Repairs in Wiring Systems. For an intermittent, refer to Intermittent Conditions. When commanding the AIR system ON with a scan tool, the PCM will activate the AIR pump and the AIR solenoid. The fuel control system will then enter an Open Loop status. This action will allow fresh air to enter the exhaust stream and cause the HO2S mV parameters to drop to near 0 mV. This would indicate a properly operating system. However, if the AIR pump does not operate, or there is no air flow from the pump entering the exhaust stream due to a leak in the system, the HO2S parameter may still drop below 100 mV. This is due to fresh air being drawn into the exhaust stream from the check valve operation and the opening of the shut-off valve. The HO2S will respond with a drop in mV readings as a result of this air leaning out the exhaust gases. The voltages may drop below 100 mV, but not approach the near 0 mV parameter. An AIR pump which exhibits an exhaust noise through the pump may have an AIR solenoid or AIR shut-off valve stuck open. The short term fuel trims may indicate a higher than normal value. This condition may not set a DTC P0410. An AIR shut-off valve that has become inoperative and has shown indications of exhaust gases in the outlet port, or heat damaged hoses may indicate an exhaust check valve failure. The vacuum lines at the vacuum solenoid cannot be reversed. This condition may hold the shut-off valve open continually. The center port of the vacuum solenoid is the vacuum source. A vacuum solenoid leaking vacuum will hold the shut-off valve open. An exhaust noise may be heard through the air cleaner. Fuel trim values may also indicate a higher than normal value at idle. This DTC may not set. Leaking check valves will leave traces of exhaust carbon in the AIR system, with a possibility of heat damage to the hoses and shut-off valve. Test Description The numbers below refer to the step numbers on the diagnostic table. This step will determine if the AIR system is functioning correctly. This step determines if there is a short to voltage on the AIR pump supply voltage circuit. Allowing the AIR pump to operate continuously. This step is to test for a short to voltage on the AIR solenoid supply voltage circuit keeping the AIR solenoid ON at all times. Roy - mastertech6371
Brilliant answer Roy! - patrick mannion
http://www.chinasinoy.com/service/how-to-understand-trouble-codes-37.html this obd2 trouble code table help you understand the meaning of code, and for this code: this may be covered under the emissions warranty on the vehicle. If your vehicle is out of bumper-to-bumper warranty, check if the emissions warranty is still valid! Replace the AIR pump AND one-way check valve Test and clean the AIR pump AND test and replace the one-way air check valve Replace the AIR pump inlet hose Replace the AIR pump fuse (found under the hood) - chinasinoy
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