Heated Oxygen Sensor Ho2S Signals (V6 Only)
DTC P1128 DETECTION CONDITION AND POSSIBLE CAUSE
| DTC P1128 |
HEATED OXYGEN SENSOR HO2S SIGNALS |
| DETECTION CONDITION |
- P1128 indicates that during KOER testing the front HO2S signal(s) response for a fuel shift to the correct engine bank was not indicated.
|
| POSSIBLE CAUSE |
- Crossed HO2S harness connectors.
- Crossed wiring at HO2S harness connectors.
- Crossed wiring at 104-pin PCM harness connector.
- Poor terminal connection.
|
| HINT |
HO2S Sensor Description
- Detects the presence of oxygen in the exhaust and produces a variable voltage (0.0 -1.1 V) according to the amount of oxygen detected.
- A high concentration of oxygen (lean air/fuel ratio) in the exhaust produces a low voltage signal (less than 0.4 V).
- A low concentration of oxygen (rich air/fuel ratio) in the exhaust produces a high voltage signal (greater than 0.6 V).
- Provides feedback to the PCM indicating air/fuel ratio in order to achieve a near stoichiometric air/fuel ratio of 14.7:1 during closed loop engine operation.
|
 Courtesy of MAZDA MOTORS CORP.
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DTC P1128 INSPECTION
| STEP |
INSPECTION |
ACTION |
| 1 |
- Was PCM Quick Test performed?
|
Yes |
Go to next step. |
| No |
Perform PCM Quick Test. |
| 2 |
KOER DTC P1128
- Visually inspect vehicle front HO2S harness connector(s) for any indication of being crossed (stretched wires, wire harnesses not mounted properly).
- Are there crossed connections or wires?
|
Yes |
Repair as necessary.
Go to step 4. |
| No |
Go to next step. |
| 3 |
VERIFY PROPER HO2S SIG PIN LOCATION
- Disconnect PCM.
- Install Breakout Box, leave PCM disconnected.
- Disconnect both of the front HO2S sensors from the vehicle harness connector.
- HO2S-11 (Front RH) = test pin 60
- HO2S-21 (Front LH) = test pin 87
- Measure the resistance of HO2S signal circuits between PCM test pins and HO2S harness connector.
- Is the resistance less than 5.0 ohms?
|
Yes |
Unable to duplicate or identify fault at this time.
See
TEST 4: INTERMITTENT
. |
| No |
Reconnect HO2S connector to proper HO2S signal pins in the PCM 104-pin harness or HO2S harness connectors.
Go to step 4. |
| 4 |
VERIFY TROUBLESHOOTING OF DTCs COMPLETED
- Make sure to reconnect all disconnected connectors.
- Clear DTCs from PCM memory using NGS tester generic OBD-II function.
- Perform PCM Quick Test.
- Is same DTC present?
|
Yes |
Replace PCM. See COMPUTERIZED ENGINE CONTROLS
.
Repeat PCM Quick Test. |
| No |
If any other DTC is present, go to applicable DTC inspection.
If no DTC is present, troubleshooting complete. |