P1134

DTC P1134 HO2S - Transition Time Ratio Bank1 Sensor1




Circuit Description

IMPORTANT: If the voltage is measured with a 10 Megohm DMM, the voltage may read as low as 0.32 volt.

The HO2S does not produce a voltage at temperatures below 200 °C (392 °F). When the HO2S is below 200 °C (392 °F), the VCM will default to a 450 mV reference voltage. When the HO2S temperature is below 200 °C (392 °F), the oxygen sensor voltage displayed on the scan tool will be near the 450 mV reference signal. The VCM holds the fuel control system in open loop operation until the sensor reaches operating temperature. The HO2S heater provides for a faster sensor warm-up which allows the sensor to become active in a shorter period of time. When the HO2S temperature exceed 200 °C (392 °F), the sensor begins producing a voltage that varies in response to exhaust oxygen levels. This voltage ranges from a high of approximately 900 mV under rich exhaust conditions, to a low of approximately 100 mV under lean exhaust conditions. These voltage transitions from rich-to-lean and lean-to-rich occur rapidly when the VCM is in control of the air/fuel ratio (closed loop operation).

This DTC determines if the difference in transition times from lean to rich or rich to lean has exceeded a maximum ratio. The VCM monitors the time it takes for the HO2S to transition from (above 600 mV) to a lean (below 300 mV) and vice versa. If either of these times is longer than the other by a calibrated ratio, this DTC will set.

Conditions for Running the DTC
- No active TP sensor DTCs
- No active EVAP system DTCs
- No active IAT sensor DTCs
- No active MAP sensor DTCs
- No active ECT sensor DTCs
- No active MAF sensor DTCs
- No active misfire DTCs
- No intrusive tests in progress
- The system voltage is between 11.7 - 18 volts.
- DTCs P0131, P0132, P0134, and P0135 not active
- The system is in closed loop.
- The ECT is greater than 57 °C (135 °F).
- The engine has been running for more than 75 seconds.
- The MAF is between 15 - 55 g/s.
- The engine speed is between 1100 - 3000 RPM.
- The EVAP canister purge is active.
- The above conditions are present for more than 2 seconds.

Conditions for Setting the DTC
The average transition time over a 100 second sample period is not within a specified range.

Action Taken When the DTC Sets
- The VCM illuminates the MIL (Malfunction Indicator Lamp) if a failure is detected during 2 consecutive key cycles.
- The VCM will set the DTC and records the operating conditions at the time the diagnostic fails. The VCM stores the failure information in the scan tools Freeze Frame and/or the Failure Records.

Conditions for Clearing the MIL/DTC
- The VCM turns OFF the MIL after 3 consecutive drive trips when the test has Run and Passed.
- A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles (coolant temperature has risen 22 °C (40 °F) from the startup coolant temperature and the engine coolant temperature is more than 70 °C (158 °F) during the same ignition cycle).
- Use the scan tool Clear Information function.

Diagnostic Aids

IMPORTANT: Never solder the HO2S wires. For proper wire and connector repairs, refer to Wiring . Repairs or Connector Repairs.

Check for the following conditions:
- An improperly installed air cleaner outlet duct
- The air cleaner outlet duct for collapsed ducting, restrictions, or a missing or plugged air filter
- Throttle Body and intake manifold vacuum leaks
- A damaged or blocked throttle Body inlet
- Exhaust system for corrosion, leaks, or loose or missing hardware. Refer to Exhaust System Inspection in Engine Exhaust
- The HO2S is installed securely and the pigtail harness is not contacting the exhaust manifold or wires
- HO2S contamination
- The vacuum hoses for splits, kinks, and proper connections
- Excessive water, alcohol, or other contaminants in the fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis
- VCM sensor grounds that are clean, tight, and properly positioned

An intermittent may be caused by any of the following conditions:
- A poor connection
- Rubbed through wire insulation
- A broken wire inside the insulation

Thoroughly check any circuitry that is suspected of causing the intermittent complaint. Refer to Intermittents and Poor Connections Diagnosis.

If a repair is necessary, then refer to Wiring Repairs or Connector Repairs.

Steps 1 - 3:

Steps 4 - 6:

Steps 7 - 9:

Steps 10 - 13:

Steps 14 - 18:

Test Description
The number below refers to the step number on the diagnostic table.
2. HO2S contamination is indicated if multiple Response, Switching or Time Ratio HO2S DTCs are set.
4. The use of leaded fuel may be indicated by the removal or tampering of the fuel filler restrictor.
An HO2S contaminated by silicon will have a white, powdery deposit on the portion of the HO2S that is exposed to the exhaust stream. The usual cause of silica contamination is the use of un-approved silicon RTV engine gasket material or the use of silicon based sprays or fluids within the engine.
If the cause of this contamination is not corrected, the replacement HO2S will also get contaminated.
7. Even small exhaust leaks can cause slow response from the HO2S.
12. An HO2S contaminated by silicon will have a white, powdery deposit on the portion of the HO2S that is exposed to the exhaust stream. The usual cause of silica contamination is the use of un-approved silicon RTV engine gasket material or the use of the use of silicon based sprays or fluids within the engine. If the cause of this contamination is not corrected, the replacement HO2S will also get contaminated.
13. If the voltage observed in step 8 is less than the range specified a short between the HIGH and LOW circuits or a short between the HIGH circuit and ground is indicated. With the HO2S and the VCM disconnected the resistance between the HIGH and LOW circuits and the resistance between the HIGH circuit and ground should measure infinite.
If the voltage observed in step 8 is greater than the range specified a short between the HIGH circuit and an ignition voltage source is indicated.
14. If the voltage observed in step 9 is not below the voltage specified a high resistance (open) HIGH or LOW circuit is indicated.

Good circuit continuity measures less than 5 ohms with the VCM and sensor disconnected. Measure between the VCM connector and the HO2S connector. Ensure VCM terminal contact is good.