P0172

DTC P0172 System Too Rich (Bank 1)

DESCRIPTION

In order to provide the best possible combination of drivability, fuel economy and emission control, the ECM uses a closed loop air/fuel metering system. The ECM monitors the HO2S signal voltage and adjusts fuel delivery based it in closed loop fuel control Changes in fuel delivery will be indicated by the long-term and the short-term fuel trim values. The ideal fuel trim value is around 0%. The ECM will add fuel when the HO2S signal is indicating a lean condition Additional fuel is indicated by fuel trim values that are above 0%. The ECM will reduce fuel when the HO2S signal is indicating a rich condition. Reduction in fuel is indicated by fuel trim values that are below 0%. The DTC relevant to fuel trim will be set when the amount reaches excessive levels because of a lean or rich condition.

Detecting Condition & Limp Home:

DTC DETECTING CONDITION

1. DTC Description
Breaking the lambda adaptation and lambda controller limits for a long time, which may have been caused by failures in the fuel or intake system will involve emission rise and therefore shall be diagnosed by fuel system monitoring. The lambda controller deviation including adaptive terms are used for fuel system monitoring. The time counter is increased if lambda controller exceeds the threshold and the ECM sets DTC P0171 or P0172 respectively depending on direction of lambda controller deviation. P0171 is set with positive deviation and P0172 is set with negative deviation. If same error code is set in the next driving cycle, the ECM illuminates the MIL.

2. Conditions for Setting the DTC

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Inspection Procedure