Circuit Description
The DTC P0135 HO2S Heater Performance Sensor 1 diagnostic monitors the operation of the heater of the HO2S 1. The heated oxygen sensors (HO2S) increase the amount of time the sensor spends in closed loop fuel control operation or catalyst monitoring operation. The oxygen sensor heater greatly reduces the amount of time required for the fuel control HO2S (sensor 1) to become active. The oxygen sensor heater is required by the post-catalyst HO2S (sensor 2) in order to maintain the high operating temperatures. The heater helps provide accurate oxygen content readings of the engine exhaust by the HO2S.
Condition for Running the DTC
The ignition is ON or the engine is running.
Conditions for Setting the DTC
| • | Current of the HO2S heater is more than 5.3 amps or less than 0.15 amps when the heater is ON. |
| • | Voltage of the HO2S heater is more than 13.80 volts or lower than 8.7 volts when the heater is ON. |
| • | Voltage of the HO2S heater is 6 volts, with the heater OFF. |
| • | One of the above conditions is present for 3 seconds. |
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL) after two consecutive ignition cycles in which the diagnostic runs with the fault active. |
| • | The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer. |
Conditions for Clearing the MIL/DTC
| • | The MIL turns OFF after three consecutively passing trips without a fault present. |
| • | A History DTC clears after 40 consecutive warm-up cycles without a fault. |
| • | Use the scan tool Clear DTC Information function or disconnect the PCM battery feed in order to clear the DTC. |
Diagnostic Aids
If a DTC P0135 is intermittent, driving the vehicle under the conditions outlined in the Inspection/Maintenance (I/M) section can verify whether the fault is present. Refer to Inspection/Maintenance Heated Oxygen Sensor Heater System Set .
An intermittent malfunction may be caused by a problem in the HO2S 2 sensor electrical circuit. Inspect the wiring harness and components for an intermittent condition. Refer to Intermittent Conditions .
If you cannot duplicate the DTC P0135, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.
Test Description
The numbers below refer to the step numbers in the diagnostic table.
-
The Diagnostic System Check-Engine Controls prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
-
This step measures the resistance of the heater circuit of the HO2S. The resistance of the HO2S used on a vehicle equipped with a Warm-Up Three-Way Catalytic (TWC) converter is about half the value of a vehicle equipped without a TWC converter.
-
The PCM turns ON the HO2S heater when the engine is running. A test lamp that is ON steady or flashing, indicates that the HO2S heater control circuit is OK.
-
This step checks whether the malfunction that caused the DTC P0135 is still present. Driving the vehicle under these conditions will verify whether the fault is present. After performing the scan tool clear DTC information function, the DTC P0135 diagnostic can be monitored on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If DTC P0135 appears in the Not Ran Since Code Cleared list, the P0135 diagnostic has not yet run. When DTC P0135 does not appear in the Not Ran Since Code Cleared list, the P0135 diagnostic has run. If the MIL is NOT illuminated and there is no Pending DTC Status in DTC Information, the P0135 diagnostic has passed. The DTCs MUST be cleared in order to view the Current Status of the Not Ran Since Code Cleared list. DO NOT forget that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for Current or Pending status in order to determine the outcome of the diagnostic test involved.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||
Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | ||
2 |
Does the test lamp illuminate? | -- | Go to Step 3 | Go to Step 7 |
Is the HO2S heater resistance within the specified range? | HO2S with Warm-Up TWC 4.5-5.7 ohms at 20°C (68°F) HO2S without Warm-Up TWC 11.7-15.6 ohms at 20°C (68°F) | Go to Step 4 | Go to Step 8 | |
Did the test lamp illuminate only when the engine was running? | -- | Go to Diagnostic Aids | Go to Step 5 | |
5 |
Is the voltage more than the specified value? | 10 V | Go to Step 10 | Go to Step 6 |
6 | Repair the open circuit or the short to ground in the HO2S heater control circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 11 | -- |
7 | Repair the open in the ignition positive voltage circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 11 | -- |
8 |
Was a repair necessary? | -- | Go to Step 11 | Go to Step 9 |
9 | Replace the HO2S 1. Refer to Heated Oxygen Sensor 2 Replacement . Did you complete the replacement? | -- | Go to Step 11 | -- |
10 |
Important: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 11 | -- |
Does the DTC run and pass? | -- | Go to Step 12 | Go to Step 2 | |
12 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
