P0135
DTC P0135: HO2S Heater Performance Sensor 1Wiring Diagram:
Circuit Description
In order to control emissions, a catalytic converter is used to convert harmful emissions into harmless water vapor and carbon dioxide.
The Engine Control Module (ECM) has the ability to monitor this process by using a HO2S1. The HO2S1, located in the exhaust stream past the catalytic converter, produces an output signal which indicates the storage capacity of the catalyst, this in turn indicates the catalyst ability to convert exhaust emissions effectively. If the catalyst is functioning properly, the HO2S2 signal will be far less active than the signal produced by the HO2S1.
If the HO2S1 pigtail wiring, connector or terminal are damaged, the entire HO2S1 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 HO2S1 wire(s). Any attempt to repair the wires, connector or terminals could result in the obstruction of the air reference and degrade HO2S1 performance.
Conditions for Setting the DTC
- Engine run time is greater than 60 seconds.
- Heater duty cycle commanded is greater than 0.1%.
- Max-Min commanded duty cycle is less than 0.05%.
- Filtered O2 heater current is greater than 0.025 A.
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 Diagnostic Trouble Code (DTC) is stored.
Conditions for Clearing the MIL/DTC
- The MIL will turn OFF after three 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 DTC(s) can be cleared by using the scan tool.
Diagnostic Aids
An intermittent may be caused by rubbed through wire insulation or a wire contacting the exhaust.
Check for poor connection or damaged harness - inspect harness connectors for the following conditions:
- Improper mating
- Broken locks
- Improperly formed
- Damaged terminals
- Poor terminal-to-wire connection
- Damaged harness
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
1. The On-Board Diagnostic (OBD II) 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.
2. This step determines if DTC P0135 is the result of a hard failure or an intermittent condition. With the ignition ON, engine OFF, the HO2S1 voltage displayed on the scan tool should change within several minutes toward 0 or 1 V, indicating that the heater is working properly.
3. Probing terminal 1 of the HO2S1 connector verifies if voltage is available to the HO2S1 heater.
4. If voltage is available at the connector, than it becomes a good voltage source to check for a ground at terminal 4.
5. Determines if voltage is not available at the HO2S1 due to an open in the HO2S1 fuse or open ignition feed circuit. If the fuse is open, determine if it was due to a short in the ignition feed circuit before replacing the fuse.
Step 1-14:
Troubleshooting