O2 sensor DTC problems
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Lambda probe reads presence of oxygen in the exhaust gases, and generates a voltage signal proportional to the amount of oxygen. the reading of a constant low or high voltage on the lambda probe, as well as very slow or no voltage |
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The voltage signal can vary from approximately 0.1 to 0.9V. Low voltage indicates the lean mixture and the high voltage rich mixture. When the engine is at operating temperature (Closed Loop) the ECU uses the voltage signal to balance the mixture. Faulty sensor will disable the Closed Loop, and the result will be increased fuel consumption.
Constant low voltage signals can cause the occurrence of DTC, which indicates a malfunction of the probe.
However, the cause of the low signal value may lie in damaged vacuum hoses connected to the engine intake manifold.
The entry of additional volume of air will pauperize the mixture and automatically increase the amount of oxygen in the exhaust gases.
However, the cause of the low signal value may lie in damaged vacuum hoses connected to the engine intake manifold.
The entry of additional volume of air will pauperize the mixture and automatically increase the amount of oxygen in the exhaust gases.
The same case we shall have if there is a damaged gasket on intake manifold, as well as on exhaust manifold. The misfire of one or more cylinders or a burnt exhaust valve can also be cause of excessive oxygen in the exhaust gases.
In both last cases, the unburned gases will increase the amount of oxygen in the exhaust gases.
In both last cases, the unburned gases will increase the amount of oxygen in the exhaust gases.
Test of the O2 sensor has to be done by reading the voltage oscillation when suddenly fuel-air mixture is changed.
Apart from reading voltage value with voltmeter, this option is provided in every OBD II program. When the engine is at operating temperature, disconnect a vacuum hose from the engine inlet manifold.
The value of voltage at the test must fall sharply and quickly. Small, slow or no change in voltage certainly indicates a malfunction of the probe. If, in addition to the O2 sensor, trouble codes are also related to the MAP sensor and the occasional misfire, problem usually lies in a serious vacuum leak from the intake manifold. Vacuum leakage which is often the cause of mentioned problems usually is present.
only during the engine operation at idle. Checking the vacuum leaks can
Apart from reading voltage value with voltmeter, this option is provided in every OBD II program. When the engine is at operating temperature, disconnect a vacuum hose from the engine inlet manifold.
The value of voltage at the test must fall sharply and quickly. Small, slow or no change in voltage certainly indicates a malfunction of the probe. If, in addition to the O2 sensor, trouble codes are also related to the MAP sensor and the occasional misfire, problem usually lies in a serious vacuum leak from the intake manifold. Vacuum leakage which is often the cause of mentioned problems usually is present.
only during the engine operation at idle. Checking the vacuum leaks can
sometimes give a real headache, especially if there is a small leak. In the number of cases, vacuum leak is not visible or hearable. Apart from the described possibilities, the vacuum leak can be expected on the worn fuel injector seals, which are usually inaccessible for inspection.
In certain cases we can use WD 40 spray for finding smaller leaks. Spraying vacuum connections when engine is running,
In certain cases we can use WD 40 spray for finding smaller leaks. Spraying vacuum connections when engine is running,
we can hear and see the entry of fluid into the intake manifold. Moreover, when we encounter a vacuum leak with spray, the engine RPM will change for a moment.
