This diagnostic applies only to vehicles built with Delphi heated oxygen sensors. In order to identify the heated oxygen sensor, refer to
The powertrain control module (PCM) supplies a voltage of about 450 mV between the heated oxygen sensor (HO2S) high and low signal circuits. The HO2S varies the voltage over a range of about 1,000 mV when the exhaust is rich to about 10 mV when the exhaust is lean.
The PCM monitors and stores the HO2S voltage information. The PCM evaluates the HO2S voltage samples in order to determine the amount of time the HO2S voltage was out of range. The PCM compares the stored HO2S voltage samples taken within each sample period and determines if the majority of the samples are out of the operating range.
The PCM monitors the HO2S voltage for being fixed below a predetermined voltage. If the PCM detects the voltage is below a predetermined voltage, a diagnostic trouble code (DTC) sets.
The HO2S voltage is less than 200 mV for 165 seconds.
Important: Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing or replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the PCM.
For an intermittent condition, refer to Intermittent Conditions .
The numbers below refer to the step numbers on the diagnostic table.
If the voltage is below the specified value the condition is present.
Jumpering the HO2S low signal circuit to ground is necessary for the PCM to correctly measure the voltage on the HO2S high signal circuit. If the HO2S voltage is within the specified range, the PCM and HO2S high signal circuit are OK.
Step
Action
Value(s)
Yes
No
Schematic Reference: Engine Controls Schematics
Important: This diagnostic applies only to vehicles built with Delphi heated oxygen sensors. To identify the heated oxygen sensor, refer to
1
Did you perform the Diagnostic System Check-Engine Controls?
--
Go to Step 2
Go to Diagnostic System Check - Engine Controls
2
Is the HO2S voltage less than the specified value?
200 mV
Go to Step 4
Go to Step 3
3
Does the DTC fail this ignition?
Go to Diagnostic Aids
4
Is the HO2S voltage within the specified range?
350-550 mV
Go to Step 5
Go to Step 6
5
Did you find and correct the condition?
Go to Step 12
Go to Step 8
6
Go to Step 7
7
Test the HO2S high signal circuit for a short to the HO2S Low signal circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Go to Step 9
8
Inspect for poor connections at the harness connector of the HO2S. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Go to Step 10
9
Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Go to Step 11
10
Replace the affected HO2S. Refer to Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 or refer to Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 .
Did you complete the replacement?
11
Replace the PCM. Refer to Powertrain Control Module Replacement .
12
Does the DTC run and pass?
Go to Step 13
13
With a scan tool, observe the stored information, Capture Info.
Does the scan tool display any DTCs that you have not diagnosed?
Go to Diagnostic Trouble Code (DTC) List
System OK
This diagnostic applies only to vehicles built with Denso heated oxygen sensors. In order to identify the heated oxygen sensor, refer to
Important: Never solder the HO2S wires. For proper wire and connection repair, refer to Wiring Repairs in Wiring Systems.
Using the scan tool, observe the long term fuel trim values at the different RPM and the air flow conditions. The scan tool also displays the fuel trim cells, so the long term fuel trim values can be checked in each of the cells in order to determine when the DTC may have set. If the conditions for this DTC exist, the long term fuel trim values measure around 158 or more.
Check for the following conditions:
An intermittent may be caused by any of the following conditions:
Thoroughly check any circuitry that is suspected of causing the intermittent complaint. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
If a repair is necessary, then refer to Wiring Repairs or Connector Repairs in Wiring Systems.
The number below refer to the step number on the diagnostic table.
Monitor the HO2S voltage of the opposite bank sensor. If the voltage activity of the opposite bank sensor is similar to the voltage activity of the suspect sensor, check for lean conditions that would affect both cylinder banks. An opposite bank sensor with normal HO2S voltage activity indicates the suspect HO2S needs replacement or a lean condition exists only on the suspect HO2S cylinder bank.
Values
Important: This diagnostic applies only to vehicles built with Denso heated oxygen sensors. To identify the heated oxygen sensor, refer to
The condition that set this DTC is not present. This DTC may have been set by one of the following conditions:
351-551 mV
Is the resistance infinite on both circuits?
∞
Repair the HO2S signal high circuit for a short to ground or a short to the HO2S low reference circuit. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?
Does the scan tool display any additional undiagnosed DTCs?