Circuit Description
The engine control module (ECM) supplies a voltage of about 0.45 volts between terminals A12 and A27. If measured with a 10 megohm digital voltmeter, this may read as low as 0.32 volts. The oxygen sensor (O2S) varies the voltage within a range of about 1 volt if the exhaust is rich, down through about 0.1 volts if the exhaust is lean.
The sensor is like and open circuit and produces no voltage when it is below 315°C (600°F). An open sensor circuit or cold sensor causes open loop operation.
If the O2S pigtail wiring, connector, or terminal is damaged, the entire O2S assembly must be replaced. Do not attempt to repair the wiring, connector, or terminals. In order for the sensor to function properly, it must have a clean air reference provided to it. This clean air reference is obtained by way of the O2S wires. Any attempt to repair the wires, connector, or terminals could result in the obstruction of the air reference and degrade the O2S performance.
Conditions for Setting the DTC
| • | O2S voltage is greater than 0.952 volts. |
| • | Closed loop stoichiometry |
| • | Engine coolant temperature (ECT) is greater than 60°C (140°F). |
| • | System voltage is greater than 10 volts. |
| • | DTCs P0107, P0108, P0117, P0118, P0122, P0123, P0201, P0202, P0203, P0204, P0336, P0337, P0351, P0352, and P0443 are not set. |
| • | Three second delay after conditions are met |
Action Taken When the DTC Sets
| • | The malfunction indicator lamp (MIL) will illuminate. |
| • | The ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers. |
| • | A history DTC is stored. |
| • | The vehicle will operate in open loop. |
Conditions for Clearing the MIL/DTC
| • | The MIL will turn OFF after 4 consecutive ignition cycles in which the diagnostic runs without a fault. |
| • | A history DTC will clear after 40 consecutive warm-up cycles without a fault. |
| • | The DTCs can be cleared by using the scan tool. |
| • | Disconnect the ECM battery feed for more than 10 seconds. |
Diagnostic Aids
The DTC P0132 or rich exhaust is most likely caused by one of the following items:
| • | Fuel pressure--The system will go rich if the fuel pressure is too high. The ECM can compensate for some increase, but if it gets too high, a DTC P0132 will be set. |
| • | Leaking injector--A leaking or malfunctioning injector can cause the system to go rich causing a DTC P0132. |
| • | Manifold absolute pressure (MAP) sensor--An output that causes the ECM to sense a higher than normal manifold pressure, low vacuum, can cause the system to go rich. Disconnecting the MAP sensor will allow the ECM to substitute a fixed value for the MAP sensor. Substitute a different a MAP sensor if the rich condition is gone while the sensor is disconnected. |
| • | Pressure regulator--Inspect for a leaking fuel pressure regulator diaphragm by inspecting for the presence of liquid fuel in the vacuum line to the regulator. |
| • | TP sensor--An intermittent TP sensor output will cause the system to go rich due to a false indication of the engine accelerating. |
| • | O2S contamination--Inspect the O2S for silicone contamination from fuel or the use of improper room temperature vulcanizing (RTV) sealant. The sensor may have a white powdery coating which may result in a high but false voltage signal, rich exhaust indication. The ECM will then reduce the amount of fuel delivered to the engine, causing a severe surge or driveability problem. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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The On-Board Diagnostic System Check prompts the technician to complete some basic checks and store the Freeze Frame and Failure Records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored on the scan tool for later reference.
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This step determines if DTC P0132 is the result of a hard failure or an intermittent condition. It may be necessary to operate the vehicle within the Freeze Frame conditions and Conditions for Setting the DTC in order to duplicate the malfunction detected by the ECM.
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This step simulates a DTC P0131. If the ECM senses the change, the ECM and the wiring are OK.
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The replacement ECM must be reprogrammed. Refer to the latest Techline procedure for ECM reprogramming.
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If no malfunctions have been found at this point and no additional DTCs were set, refer to Diagnostic Aids in this section for additional inspections and information.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Perform an On-Board Diagnostic System Check. Was the check performed? | -- | Go to Step 2 | ||
Does the oxygen sensor (O2S) voltage remain less than the value specified? | 952 mV | Go to Step 4 | Go to Step 3 | |
3 |
Does the O2S voltage remain less then the specified value? | 952 mV | Go to Step 4 | Go to Step 7 |
Does the scan tool display the O2S voltage less than the specified value? | 500 mV | Go to Diagnostic Aids | Go to Step 5 | |
5 | Inspect the O2S signal circuit, terminal 2 for a short to voltage and repair as needed. Did you find and correct the condition? | -- | Go to Step 7 | Go to Step 6 |
Did you complete the replacement? | -- | Go to Step 7 | -- | |
7 |
Does the scan tool indicate that this diagnostic has run and passed? | -- | Go to Step 8 | Go to Step 2 |
Are any DTCs displayed that have not been diagnosed? | -- | Go to applicable DTC table | System OK |
