Schematic Reference: Engine Controls Schematics
Circuit Description
The PCM monitors the Heated Oxygen Sensor (HO2S) activity. During the monitor period the PCM counts the number of times that the HO2S responds 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 ratio is not within range, a DTC P1134 will be set.
Conditions for Setting the DTC
| • | DTCs P0100, P0102, P0103, P0107, P0108, P0117, P0118, P0125, P0200, P0372 not set. |
| • | System operating in Closed Loop |
| • | Engine speed greater than 1000 RPM but less than 1700 RPM. |
| • | MAF between 12 gm/s and 28 gm/s. |
| • | The PCM determines that the HO2S transition time ratio is not at the expected value. |
Action Taken When the DTC Sets
| • | The DTC will be stored in the PCM memory when the diagnostic runs and fails. |
| • | The Malfunction Indicator Lamp (MIL) will not illuminate. |
| • | The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in Failure Records. |
Conditions for Clearing the MIL/DTC
| • | A history DTC will clear after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic. |
| • | A last test failed (Current DTC) will clear when the diagnostic runs and does not fail. |
| • | PCM battery voltage is interrupted. |
| • | Using a scan tool. |
Diagnostic Aids
| • | Using Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If the DTC cannot be duplicated, the information included in the Freeze Frame and/or Failure Records data can be useful in determining how many miles since the DTC set. The Fail Counter and Pass Counter can also be used to determine how many ignition cycles the diagnostic reported a pass and/or a fail. Operate vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that were noted. This will isolate when the DTC failed. |
| • | An oxygen supply inside the HO2S is necessary for proper operation. This supply of oxygen is provided through the HO2S wires. All HO2S wires and connections should be inspected for breaks or contamination. Refer to Repair Procedures in Electrical Diagnosis (8A Cell 5). |
For intermittents, refer to Symptoms .
Test Description
Number(s) below refer to step numbers on the diagnostic table.
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Determines if the fault is present. This test may take 5 minutes for the diagnostic to run.
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When DTCs P1134 and P1154 are set at the same time, is good indication that a fuel contamination problem is present.
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An exhaust leak 6 to 12 inches away from the HO2S can cause a DTC to set.
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Checks whether a good ground circuit is available.
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Checks the integrity of the signal circuit to the PCM.
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Certain RTV silicone gasket materials give off vapors that can contaminate the HO2S. There is also a possibility of silicone contamination caused by silicone in fuel. If it appears that the sensors are contaminated by silicon and all silicone sealant is a none silicone base, advise customer to try a different fuel company. A fuel filler restrictor missing, indicates leaded fuel may have been used.
Step | Action | Value(s) | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||||||||||
|
Important: If any DTCs are set (Except P1153), refer to those DTCs before proceeding with this diagnostic table.
Does the scan tool indicate DTC P1133 test failed? | -- | Go to Diagnostic Aids | ||||||||||
Did the scan tool also indicate P1153 test failed? | -- | |||||||||||
Was an exhaust leak isolated? | -- | |||||||||||
5 | Visually/physically inspect the following items:
Was a problem found in any of the above areas? | -- | ||||||||||
Does the scan tool indicate voltage within specified values? | 375-525 mV | |||||||||||
7 |
Does the scan tool indicate voltage below specified value? | 200 mV | ||||||||||
|
Important: Before replacing a sensor, the cause of the contamination must be determined
and corrected. Check for the following conditions:
Replace the affected Heated Oxygen Sensor. Refer to Heated Oxygen Sensor Replacement . Is the action complete? | -- | -- | ||||||||||
9 | Repair the condition as necessary. Is the action complete? | -- | -- | |||||||||
10 | Repair the open Bank 1 HO2S 1 low signal circuit or grounded Bank 1 HO2S 1 high signal circuit. Is the action complete? | -- | -- | |||||||||
11 | Repair the open Bank 1 HO2S 1 high signal circuit or faulty PCM connections. Is the action complete? | -- | -- | |||||||||
12 | Replace Bank 1 HO2S 1. Refer to Heated Oxygen Sensor Replacement . Is the action complete? | -- | -- | |||||||||
13 |
Does the scan tool indicate that this test ran and passed? | -- | ||||||||||
14 | Using the scan tool, select Capture Info, Review Info. Are any DTCs displayed that have not been diagnosed? | -- | Go to the applicable DTC table | System OK |
