What is code po492 mean?

 

See if this helps...

http://www.stengel.net/diccodes.htm

 

not on there I already looked there

 

What Year?

 

2004 z06

 

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.
Diagnostic Aids
For any test that requires probing the PCM or probing a component harness connector, use the connector test adapter kit . Using this kit prevents damage to the harness or component terminals. Refer to in Wiring Systems.
Carbon build-up in the exhaust manifold may restrict the amount of air flow necessary to affect the HO2S voltage. If you suspect this condition, remove the air pipe from the manifold and inspect the passage.
For an intermittent condition, refer to .
Inspect for the following conditions:
Excessive exhaust system back pressure
Moisture, water, or debris ingestion into the AIR pump
Leaking exhaust check valves will leave traces of exhaust carbon in the AIR system.
A check valve that flows in both directions causes heat damage to the AIR system components.

 

Thanks

 

My '04 just threw that one again after a year. The general problem is with the secondary air system check valves. There are two, one on the driver's side of the engine, and one behind the driver's side engine head.
Guess which one is the general problem one! Right, the difficult to reach one. I was happy last year to hear about the WD 40 trick. By spraying the WD into the system and running it a bit, it frees up the stuck valve and the code does not re-occur. If you do a search you will see a lot on this, even someone has disected one.
I am not looking forward to replacing it though, it probably is not expensive, but real tough to get at.

 

help me here, i read spraying the WD-40 into the system, where do you spray the WD-40, into what system?

 

Help me out here, I read spraying the WD-40 into the system, where do u spray the WD & into what system?

 

Alright, check this out.
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http://forums.corvetteforum.com/c5-t...eck-valve.html

 

I updated the post with some c0ol info on why the valves fail. Check it out. The rubber diaphrams inside the valves get hard and stiff. Cleaning works sometime if the rubber diaphram sticks to the seat but, if the disk is hard, its time fo a new one. When they get hard, they will flow air but jut not enough air to allow the PCM to see the changes in the O2 sensor output.

 

great write up Im not touching it since its still covered on my car