Circuit Description
The PCM supplies a bias voltage of about 450 mV between the HO2S signal and low circuits. When measured with a 10 megohm digital voltmeter, this may display as low as 320 mV. The oxygen sensor varies the voltage within a range of about 1000 mV when the exhaust is rich, down through about 10 mV when exhaust is lean. The PCM constantly monitors the HO2S signal during closed loop operation and compensates for a rich or lean condition by decreasing or increasing injector pulse width as necessary. If the Bank 2 HO2S 1 voltage remains excessively high for an extended period of time, DTC P0152 will be set.
Conditions for Setting the DTC
| • | No active transmission, TP sensor, EVAP system, misfire, IAT sensor, MAP sensor, fuel trim, fuel injector circuit, EVAP solenoid ODM, ECT sensor, or MAF sensor DTC(s) present. |
| • | Air/Fuel ratio is between 14.5 to 1 and 14.8 to 1. |
| • | Throttle position is between 3% and 40%. |
| • | Engine has been running for at least 2 minutes and is in closed loop. |
| • | Engine speed is between 1,000 RPM and 3,000 RPM. |
| • | Engine Coolant Temperature greater than 75°C (167°F). |
| • | Mass Air Flow between 15 gm/s and 29 gm/s. |
| • | Above conditions must be present for a 100 second sample period. |
| • | Bank 2 H02S 1 lean to rich or rich to lean average transition response time was longer than 90 milliseconds. |
| • | Above conditions met for 5 seconds |
Action Taken When the DTC Sets
| • | The PCM will illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the diagnostic test has been run and failed. |
| • | The PCM will store conditions which were present when the DTC set as Freeze Frame and Failure Records data. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn OFF the MIL during the third consecutive trip in which the diagnostic has been run and passed. |
| • | The History DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | The DTC can be cleared by using the scan tool. |
Diagnostic Aids
Check for the following conditions:
| • | Fuel pressure high - An excessively rich fuel mixture can cause a DTC P0152 to be set. Refer to Chart A-7, Fuel System Diagnosis. |
| • | Fuel injector(s) faulty - Refer to Chart C-2A, Injector Balance Test. |
| • | Check the EVAP Canister for Fuel Saturation. If the EVAP Canister is full of fuel, check canister control and hoses. Refer to Evaporative Emission (EVAP) Control System. |
| • | Disconnect the MAF sensor and see if rich condition is corrected. If so, replace MAF sensor. |
| • | Check for a leaking fuel pressure regulator diaphragm by checking the vacuum line to the fuel pressure regulator for the presence of fuel. |
| • | An intermittent TP sensor output will cause the system to go rich, due to a false indication of the engine accelerating. |
| • | Shorted HO2S - If the HO2S is internally shorted the HO2S voltage displayed on the scan tool will be over 1 volt. Try disconnecting the affected HO2S and jumper the HO2S low circuit to ground with the key ON. If the displayed HO2S voltage changes from over 1000 mV to around 450 mV, replace the HO2S. Silicon contamination of the HO2S can also cause a high HO2S voltage to be indicated. This condition is indicated by a powdery white deposit on the portion of the HO2S exposed to the exhaust stream. If contamination is evident, replace the affected HO2S. |
| • | Open HO2S Signal or Low Circuit or Faulty HO2S - A poor connection or open in the HO2S signal or low circuit can cause the DTC to set during deceleration fuel mode. An HO2S which is faulty and not allowing a full voltage swing between the rich and lean thresholds can also cause this condition. Operate the vehicle while monitoring the HO2S voltage with a scan tool. If the HO2S voltage is limited within a range between 300 mV to 600 mV, check the HO2S signal and low circuit wiring and associated terminal connections. If the wiring and connections are OK, replace the HO2S. |
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table:
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DTC P0152 failing during deceleration fuel mode operation may indicate a condition described in the Diagnostic Aids above. If the DTC P0152 test passes while the Fail Records conditions are being duplicated, an intermittent condition is indicated. Review the Fail Records vehicle mileage since the diagnostic test last failed. This may help determine how often the condition that caused the DTC to be set occurs.
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This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||
2 |
Does the HO2S voltage remain above the specified value? | 800 mV | ||
Operate vehicle in Decel fuel mode (vehicle speed above 25 mph, TP angle below 3%) while monitoring HO2S 1 voltage display on the scan tool HO2S data list. Does the HO2S 1 voltage remain above the specified value while in Decel fuel mode? | 110 mV | |||
4 |
Does the scan tool indicate DTC P0132 failed this ignition? | -- | Go to Diagnostic Aids | |
5 | Disconnect HO2S 1 and jumper HO2S low circuit to ground. Does scan tool indicate HO2S 1 voltage near the specified value? | 450 mV | Go to Diagnostic Aids | |
6 |
Does the Digital Multimeter indicate a voltage greater than specified value? | 600 mV | ||
Repair short to voltage in the HO2S 1 signal circuit. Refer to Heated Oxygen Sensor (HO2S) Repair in Electrical Diagnosis. Is the action complete? | -- | -- | ||
8 | Replace the PCM. Important: Replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | -- | |
9 |
Does the scan tool indicate DTC P0152 failed this ignition? | -- | System OK | |
