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I got my 2004 impala diagnosis and it said I have a defective oxygen sensor and my engine is getting to much oxygen and it say low voltage to the computer plus my fuel is running very lean fuel pump defective what does this mean?

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This signal is from a sensor on the exhaust system telling the engine there is a fuel mixture problem , it may be the actual sensor gone faulty but first check all air intake hoses for signs of splits etc , because if the air going in the engine isn't correct the exhaust coming out wont be either, if all look ok i'd put a fuel addative in the tank , make sure you get one that says for catalytic converters as well as engine , this will clear away carbon deposits etc that have built up over time may have to do this twice ,requires a full tank to add to , if still getting the code after having it cleared then most likely is one of the o2 sensor 's on the exhaust, the code will tell which one , good luck and keep me posted if you wish

Posted on May 17, 2014


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SOURCE: 1995 GMC Sierra

check you ideler sensor i had the same problem on

Posted on Oct 07, 2008

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you need to change the oxygen sensor. it will soon cause you problems. after you need to take it in to  erase the code.

Posted on Apr 20, 2009

  • 3854 Answers

SOURCE: location of oxygen sensor

I believe you may have three (3) O2 sensor, (2) of the sensor is on ether side of the exhaust down pipe and some times called up stream O2 sensor, the third O2 sensor know to some as the down stream O2 and is after the Catalytic converter.
The up stream O2 monitors the left and right side banks and sends signals to the ECM to make the adjustments to the injectors to keep the proper air/fuel ratio. 
The down stream O2 monitors the catalytic converter and sends signal to the ECM if the catalytic converter has gone bad.
Good luck and hope this helps. If you get it scanned at Auto Zone, they should be able to let you know which O2 has gone bad so as to not change all three. You could always check the wire harness to the down stream O2 for corrosion. Keep me posted

Posted on May 29, 2009

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SOURCE: 2004 GMC Envoy.Check engine soon

This code indeed does indicate a bad thermostat, but not in a way as overheating but the coolant temperature is not rising fast enough at warm up because the stat is always in the open position.

The rushing air sound you heard was most likely the electronic fan clutch starting to go bad. This is a common problem.

Posted on Nov 24, 2010

  • 17970 Answers

SOURCE: heated oxygen sensor-bank1 sensor2 [ho2s12] circuit

HO2-S12 (Oxygen sensor 1 Bank 2) it is screwed into the exhaust system downstream (tailpipe side) of the catalytic converter.

We dont know exactly the "code number" of your description, but we could advance that is refer at bad O2 sensor in this position. Possible causes:
Contaminated HO2S.
Exhaust leaks.
Shorted/open wires.
Improper fueling.
MAF sensor.
Deteriorating HO2S.
Air leaks.

This specific Diagnostic Trouble Codes (DTCs) indicate the response rate of the upstream HO2S(s) is below some calibrated window. The test measures the HO2S amplitude and output frequency. This is accomplished by superimposing a 1.5 to 2.5 Hz square wave over Lambse. The HO2S switching is monitored during this time to see if the calibration limit is met.

Additionally, some models have a secondary air injection (AIR) system is designed to lower the exhaust emission levels after engine start up. The Powertrain Control Module (PCM) commands the AIR pump relay ON by supplying a ground to the relay control circuit. This action energizes the AIR pump which forces fresh air into the exhaust stream. The PCM also commands the AIR vacuum control solenoid valve ON by supplying a ground to the control circuit. With the AIR solenoid activated, engine vacuum is then applied to the AIR shut-off valves. Fresh air from the AIR pump then enters into the exhaust stream. The air that is introduced into the exhaust system accelerates catalyst operation reducing exhaust emission levels. When the AIR system is inactive, the AIR shut-off valves prevent air flow in either direction.

After a warm start up the PCM can detect an AIR system air flow fault by monitoring the heated oxygen sensors (HO2S) and short term fuel trim (FT) values. 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 PCM diagnostic will proceed with an intrusive or active test. The PCM will command the AIR system ON during Closed Loop operation. The active test will pass or fail based on the response from the HO2S. The active test consists of three tests run at 3 second intervals. A lean HO2S response indicates that the secondary AIR system is functioning properly. An increasing short term FT value also indicates a normal functioning system. The AIR diagnostic consists of the combination of the passive and the active tests. If the PCM detects that the HO2S and short term FT did not respond as expected on bank 1 and bank 2 DTC P0410 sets.

The AIR system consists of the following components:
The AIR pump
The shut-off valves
The vacuum control solenoid valve
The system pipes/hoses
The AIR pump relay, the fuses, and the related wiring

DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0130, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0150, P0151, P0152, P0153, P0154, P0155, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0300, P0335, P0336, P0351, P0352, P0353, P0354, P0355, P0356, P0357, P0358, P0412, P0418, P0506, P0507, P1133, P1134 are not set.

Passive Tests
The engine is running for more than 3 seconds .
The engine speed is more than 600 RPM .
The throttle is steady.
The engine load is less than 80 percent .
The system voltage is more than 10.5 volts .
The mass air flow (MAF) is less than 35 g/s .
The air/fuel ratio is more than 12.5:1.
The engine coolant temperature (ECT) is between 5-108.5°C (41-227°F) .
The engine coolant start up temperature (ECT) is between 5-80°C (41-176°F) .
The intake air temperature (IAT) is between 5-72.5°C (41-162°F) .
The power enrichment or the deceleration fuel cut-off (DFCO) is not active.

Active Tests
The engine is running for more than 3 seconds .
The engine speed is more than 600 RPM .
The throttle is steady.
The engine load is less than 80 percent .
The system voltage is more than 10.5 volts .
The MAF is less than 35 g/s .
The fuel system is in Closed Loop operation.
The evaporative emissions (EVAP) purge is active.
The ECT is more than 68°C (154°F) .
The vehicle speed is between 56-72 km/h (25-35 mph) .

Passive Tests:
- The HO2S voltage for both fuel control sensors is more than 470 mV for 20 seconds , 200 mV for 7 seconds on a warm start while the AIR system is commanded ON.
- The HO2S voltage for both fuel control sensors do not toggle above 600 mV for 25 seconds, 7 seconds on a warm start while the AIR system is commanded ON.

Active Test
- The AIR passive test is inconclusive or failed.
- The HO2S voltage for both fuel control sensors is more than 250 mV for three 3 second active tests.

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.

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.

NOTE: Refer to Connector Test Adapter Kit J 35616-A Notice in Service Precautions.

Reviewing the Failure Records vehicle mileage since the diagnostic test last failed may help to diagnose the condition. The information may help to determine how often the condition that set the DTC occurs.
Inspect for the following conditions:
A Low AIR system air flow may cause this DTC to set.
Any excessive exhaust system back-pressure
Any moisture, water, or debris ingestion into the AIR pump
Any restrictions in the AIR pump inlet, duct, or filter
An intermittent may be caused by any of the following conditions:
Any pinched hoses or vacuum lines
Any kinked pipes/hoses or vacuum lines
Any split pipes/hoses or vacuum lines
Any heat damaged pipes
Any deteriorated hoses or vacuum lines
Any reversed inlet and outlet hoses at the AIR pump may cause a reduced air flow. This condition may cause this DTC to set. The AIR pump inlet and outlet ports should be clearly identified on the pump.
An AIR solenoid stuck open or leaking vacuum internally may hold the shut-off valves open, an audible exhaust popping noise may be heard through the air pump inlet hose. This condition may not set a code and may cause the fuel trim parameters to indicate a high percentage value at an idle
The AIR solenoid vents the vacuum from the shut-off valves when the system is inactive. Verify proper connections of vacuum hoses, reversed connections at the AIR solenoid may cause the AIR shut-off valves to be held open.
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 open loop status. This action will allow fresh air to enter the exhaust stream and cause the HO2S mV parameter to drop to near 0 mV . This would indicate a properly operating AIR 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 the fresh air being drawn into the exhaust stream from the opening of the shut-off valves. The HO2S will respond with a drop in mv readings as a result of this air leaning out the exhaust. The voltages may decrease to below 100 mV but not approach 0 mV .
If the condition is intermittent, refer to Intermittent Conditions.






Posted on Aug 02, 2011

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