GM Service Manual Online
For 1990-2009 cars only

Object Number: 475493  Size: MF
Engine Controls Components
HO2S 1, HO2S 2
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

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 varies 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 P1134 will be set, indicating that the oxygen sensor is not responding as expected to changes in exhaust oxygen content.

Conditions for Running the DTC

    • No throttle position (TP) sensor, evaporative emission (EVAP) system, misfire, intake air temperature (IAT) sensor, manifold absolute pressure (MAP) sensor, fuel trim, injector circuit, exhaust gas recirculation (EGR) pintle position, mass air flow (MAF) sensor, engine coolant temperature (ECT) sensor, crankshaft position (CKP) sensor, or heated oxygen sensor (H02S) 1 heater circuit DTCs are set.
    • The mass air flow is between 10-30 g/s.
    • The engine coolant temperature (ECT) is more than 50°C (122°F).
    • The engine run time is more than 60 seconds.
    • The engine speed is between 1000-3000 RPM.
    • The engine is running in closed loop.

Conditions for Setting the DTC

    • The above conditions present for a 100 second monitoring period.
    • The ratio of average response times is not between 4.5-0.5.

Action Taken When the DTC Sets

    • The PCM illuminates the MIL during the second consecutive trip in which the diagnostic test runs and fails.
    • The PCM stores the conditions that 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 during the third consecutive trip in which the diagnostic runs and passes.
    • The history DTC clears after 40 consecutive warm-up cycles have occurred without a malfunction.
    • The DTC 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 the DTC to set. Check HO2S heater circuitry for intermittent malfunctions or poor connections. If the connections and wiring are OK and the DTC continues to set, replace the HO2S 1.

Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition occurs that caused the DTC to set. This may assist in diagnosing the condition.

Test Description

Numbers below refer to the step numbers on the Diagnostic Table.

  1. This step checks for conditions which may cause the DTC to set with a good heated oxygen sensor. Correct any of the described conditions if present.

  2. Before replacing the HO2S, check for silicon contamination. Refer to Silicon Contamination of Heated Oxygen Sensors Notice.

DTC P1134 - HO2S Transition Time Ratio Sensor 1

Step

Action

Values

Yes

No

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 DTCs are set (except P1133 or P1134), go to those DTCs before proceeding with this diagnostic table.

  1. Operate the vehicle within the parameters specified under Conditions for Setting the DTC.
  2. Using a scan tool, monitor the Specific DTC info for DTC P1134 until the DTC P1134 test runs.

Does the scan tool indicate DTC failed this ignition?

--

Go to Step 3

Go to Diagnostic Aids

3

  1. Check the exhaust system for leaks. Refer to Restricted Exhaust System Check .
  2. If an exhaust leak is found, repair as necessary.

Was a problem found?

--

Go to Step 11

Go to Step 4

4

Visually and physically inspect the following items:

    • Ensure that the HO2S 1 is securely installed.
    • Check for corrosion on terminals.
    • Check terminal tension at HO2S 1 and at the PCM.
    • Check for damaged wiring.

Was a problem found in any of the above areas?

--

Go to Step 8

Go to Step 5

5

  1. Disconnect the HO2S 1.
  2. Jumper the HO2S low signal circuit, which is on the PCM side, to a ground.
  3. Using a scan tool, monitor the HO2S 1 voltage.

Does the scan tool indicate voltage near the specified value?

450 mV

Go to Step 6

Go to Step 9

6

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

Does the scan tool indicate voltage less than the specified value?

300 mV

Go to Step 7

Go to Step 10

7

Replace the affected heated oxygen sensors. Refer to Heated Oxygen Sensor Replacement .

Is the action complete?

--

Go to Step 11

--

8

Repair the condition as necessary.

Is the action complete?

--

Go to Step 11

--

9

Repair the open HO2S 1 low signal circuit or grounded HO2S 1 high signal circuit. Refer to Heated Oxygen Sensor Wiring Repairs in Wiring Systems. .

Is the action complete?

--

Go to Step 11

--

10

Repair the open HO2S 1 high signal circuit or the faulty connections at the PCM. Refer to Testing for Continuity , Repairing Connector Terminals and Connector Repairs in Wiring Systems. .

Is the action complete?

--

Go to Step 11

--

11

  1. Clear the DTCs.
  2. Operate the vehicle within the parameters specified under Conditions for Setting the DTC.
  3. Using a scan tool, monitor the Specific DTC information for DTC P1134 until the DTC P1134 test runs.

Does the scan tool indicate DTC failed this ignition?

--

Go to Step 2

System OK