For 1990-2009 cars

### Circuit Description

The PCM continuously monitors the Heated Oxygen Sensor (HO2S) activity for 100 seconds. During the monitor period the PCM counts the number of times that the HO2S responds from rich to lean and from lean to rich and adds the amount of time it took to complete all transitions. With this information, an average time for all transitions can be determined. The PCM then divides the rich to lean average by the lean to rich average to obtain a ratio. If the HO2S transition time ratio is not within range, DTC P1154 will be set indicating that the oxygen sensor is not responding as expected to changes in exhaust oxygen content.

### Conditions for Setting the DTC

• | No injector, MAF sensor, TP sensor, EVAP, IAT sensor, MAP sensor, Fuel Trim, EGR, ECT sensor DTCs set

• | DTC P0135 (O2 Heater) not set

• | The engine has been running at least 2 minutes.

• | Engine speed is between 1,000-3,000 RPM.

• | Mass Air Flow is between 15-30 gm/s.

• | Engine Temperature is above 75°C (167°F).

• | Above conditions present for a 100 second monitoring period.

• | Bank 2 HO2S 1 transition time ratio is less than 0.4 or greater than 3.5.

### Action Taken When the DTC Sets

• | The PCM will illuminate the MIL during the second key cycle in which the DTC sets.

• | Open Loop fuel control will be in effect.

• | The PCM will store conditions which were present when the DTC set as Freeze Frame and Fail Records data.

### Conditions for Clearing the MIL/DTC

• | The PCM will turn the MIL OFF on the third consecutive trip cycle during which the diagnostic has been run and the fault condition is no longer present.

• | A history DTC P1154 will clear after 40 consecutive warm-up cycles have occurred without a fault.

• | DTC P1154 can be cleared by using the scan tool Clear Information function or by disconnecting the PCM battery feed.

### Diagnostic Aids

A malfunction in the HO2S heater ignition feed or ground circuit may cause a DTC P1154 to set. Check HO2S heater circuitry for intermittent faults or poor connections. If connections and wiring are OK and DTC P1154 continues to set, replace the Bank 2 HO2S 1. 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.

### Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table:

1. A condition that affects other heated oxygen sensors indicates probable contamination. To avoid damaging replacement sensors, correct the condition which caused the contamination before replacing the affected sensors.

2. This step checks for conditions which may cause the heated oxygen sensor to appear faulty. Correct any of the described conditions if present.

3. In order to avoid damaging replacement sensors, correct the condition which caused the contamination before replacing the affected sensors.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Engine Controls Schematics
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to the Powertrain On Board Diagnostic (OBD) System Check
2 | Important: If any other DTCs are set, refer to those DTCs before proceeding with this diagnostic chart.

1. Install scan tool
2. Engine idling at operating temperature
3. Operate vehicle within parameters specified under Conditions for Setting the DTC criteria included in Diagnostic Support.
4. Using a scan tool, monitor Specific DTC info for DTC P1154 until the DTC P1154 test runs.

Does scan tool indicate DTC failed this ignition?

--

Go to Step 3

Go to Diagnostic Aids

3 |

1. Perform Exhaust System Leak Test (refer to Exhaust System). After Exhaust System Leak Test has been performed, return to this diagnostic.
2. If an exhaust leak is found, repair as necessary

Was an exhaust leak isolated?

--

Go to Step 11

Go to Step 4

4 | Visually/physically inspect the following items:

• | Ensure that the Bank 2 HO2S 1 is securely installed.

• | Check for corrosion on terminals.

• | Check terminal tension (at Bank 2 HO2S 1 and at the PCM).

• | Check for damaged wiring.

Was a problem found in any of the above areas?

--

Go to Step 7

Go to Step 5

5 |

1. Disconnect Bank 2 HO2S 1 and jumper HO2S low (PCM side) signal circuit to ground.
2. Using a scan tool, monitor Bank 2 HO2S 1 voltage.

Does the scan tool indicate voltage near the specified value?

450 mV

Go to Step 6

Go to Step 8

6 |

1. Jumper Bank 2 HO2S 1 high and low (PCM side) signal circuits to ground.
2. Using a scan tool, monitor Bank 2 HO2S 1 voltage.

Does the scan tool indicate voltage below specified value?

200 mV

Go to Step 10

Go to Step 9

7 | Repair condition as necessary. Is the action complete? | -- | Go to Step 11 | --
8 | Repair an open Bank 2 HO2S 1 low signal circuit or a grounded Bank 2 HO2S 1 high signal circuit. Refer to Heated Oxygen Sensor (HO2S) Repair in Electrical Diagnosis. Is the action complete? | -- | Go to Step 11 | --
9 | Repair open Bank 2 HO2S 1 high signal circuit or faulty PCM connections. Refer to Heated Oxygen Sensor (HO2S) Repair in Electrical Diagnosis. Is the action complete? | -- | Go to Step 11 | --
10 | Replace Bank 2 HO2S 1. Refer to Heated Oxygen Sensor Replacement . Is the action complete? | -- | Go to Step 11 | --
11 |

1. Clear DTCs
2. Engine idling at operating temperature.
3. Operate vehicle within parameters specified under Conditions for Setting the DTC criteria included in Diagnostic Support.
4. Using a scan tool, monitor Specific DTC info for DTC P1154 until the DTC P1154 test runs

Does scan tool indicate DTC failed this ignition?

--

Go to Step 2

System OK