DTC Descriptors
DTC P0050: HO2S Heater Control Circuit Bank 2 Sensor 1DTC P0059: HO2S Heater Resistance Bank 2 Sensor 1
DTC P0155: HO2S Heater Performance Bank 2 Sensor 1
Diagnostic Fault Information
Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
Circuit | Short to Ground | High Resistance | Open | Short to Voltage | Signal Performance |
|---|---|---|---|---|---|
HO2S Heater Voltage Supply | Opens fuse P0030, P0036, P0050, P0053, P0054, P0056, P0059, P0060, P0102, P0134, P0135, P0140, P0141, P0154, P0155, P0160, P0161, P0443 | P0059 | P0050, P0059, P0155 | -- | P0155 |
HO2S Heater Low Control | P0050, P0056 | P0059 | P0050, P0059, P0155 | P0050, P0155 | P0155 |
Typical Scan Tool Data
Circuit | Normal Range | Short to Ground | Open | Short to Voltage |
|---|---|---|---|---|
HO2S Heater Voltage Supply | Approximately 0.20-1.5 A | 0.00 A | 0.00 A | Approximately 0.20-1.5 A |
HO2S Heater Voltage Supply | 7-100% | 7% | 7% | 7-100% |
HO2S Heater Low Control | Approximately 0.20-1.5 A | 0.00 A | 0.00 A | 0.00 A |
HO2S Heater Low Control | 7-100% | 7% | 7% | 7% |
Circuit/System Description
Heated oxygen sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content in the exhaust stream. The HO2S must reach operating temperature to provide an accurate voltage signal. A heating element inside the HO2S minimizes the time required for the sensor to reach operating temperature. Voltage is provided to the heater by an ignition voltage circuit through a fuse. With the engine running, ground is provided to the heater by the HO2S heater low control circuit, through a low side driver within the engine control module (ECM). The ECM uses pulse width modulation (PWM) to control the HO2S heater operation to maintain a specific HO2S operating temperature range.
P0050
The control module monitors the voltage on the HO2S heater low control circuit for heater fault diagnosis. If the control module detects that the HO2S heater low control circuit voltage is not within a specified range, DTC P0050 sets for HO2S 1.
P0059
The control module monitors the resistance on the HO2S heater circuit. If the control module detects that the HO2S heater circuit resistance is not within the calibrated range on a cold start, engine OFF for more than 10 hours, DTC P0059 will set for HO2S 1.
P0155
The control module determines the temperature by measuring the current flow through the heater. For diagnosis, the control module monitors the heater current with the engine running. If the control module detects that the HO2S 1 heater low control circuit current level is not within the calibrated range, DTC P0155 will set for HO2S 1.
Conditions for Running the DTC
P0050
| • | The engine is cranking or running. |
| • | The system voltage is between 10-18 volts. |
P0059
| • | The ignition is OFF for more than 10 hours. |
| • | The ECT Sensor parameter is between -30 and +45°C (-22 and +133°F) at engine start-up. |
| • | The system voltage is between 10-18 volts. |
| • | This diagnostic runs one time per valid cold start when the above conditions are met. |
P0155
| • | DTCs P0050, P0059, P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0128, P0135, P0141, P0201, P0202, P0203, P0204, P0205, P0206, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0451, P0452, P0453, P0454, P0455, P0461, P0464, P0496, P2119, P2135 are not set. |
| • | DTCs P0430 and P2A04 are not commanding fuel. |
| • | The system voltage is between 10-18 volts. |
| • | The scan tool special functions are not active. |
| • | The Engine Run Time parameter is more than 180 seconds. |
| • | The ECT Sensor parameter is at least 65°C (149°F). |
| • | The MAF sensor parameter is between 5-30 g/s. |
| • | The Engine Speed parameter is between 500-3,000 RPM. |
| • | The above conditions have been met for more than 6 seconds. |
Conditions for Setting the DTC
P0050
| • | The control module detects that the HO2S 1 heater control circuit status is incorrect for more than 2 seconds. |
| • | This diagnostic runs continuously. |
P0059
The control module detects that the HO2S 1 heater calculated resistance is not within an expected range at engine start-up for 1 second.
P0155
| • | The HO2S heater current is less than 0.31 amp or more than 1.5 amps for more than 8 seconds, twice in a 1-minute period. |
| • | The test is run 2 times per trip. |
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
Diagnostic Aids
When using a high impedance, low current draw, test lamp to load the heater circuit, the test lamp flash may be dim, the scan tool Heater Command parameter may indicate 7 percent, and the Heater parameter may indicate 0.00 amps. This is a normal condition.
Reference Information
Schematic Reference
Connector End View Reference
Electrical Information Reference
Scan Tool Reference
Circuit/System Verification
- Allow the engine to reach operating temperature.
- Engine running, verify the appropriate scan tool HO2S Heater parameter is varying between 0.5-2 amp.
Circuit/System Testing
Important: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.
- Ignition OFF, disconnect the harness connector at the appropriate HO2S.
- Ignition ON, verify that a test lamp illuminates between the appropriate HO2S heater voltage supply circuit terminal D and ground.
- Ignition ON, verify that a test lamp does not illuminate between the appropriate HO2S heater low control circuit terminal C and the HO2S heater voltage supply circuit terminal D.
- Engine running, leave the test lamp connected from the previous step. The lamp should flash or be ON steady.
- Ignition OFF, install a 30-amp fused jumper wire between the appropriate HO2S heater low control circuit terminal C and the HO2S heater voltage supply circuit terminal D.
- Engine running, verify the appropriate scan tool HO2S Heater parameter is less than 0.1 amp.
- If the ECM and all circuits test normal, replace the appropriate HO2S.
| ⇒ | If the test lamp does not illuminate, test the HO2S heater voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal and the HO2S heater voltage supply circuit fuse is open, test all components connected to the fuse and replace as necessary. |
| ⇒ | If the lamp illuminates, test the HO2S heater low control circuit for a short to ground. If the circuit tests normal, replace the ECM. |
| ⇒ | If the test lamp is not ON steady or flashing, test the HO2S heater low control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM. |
Important:
• The output driver should detect a short to voltage and turn OFF. If a resistance fault is present the driver will remain ON and the scan tool will display more than 0.0 amp. Less than 10 ohms of resistance may set a DTC. • Performing this test may set additional DTCs.
| ⇒ | If more than the specified range, test the HO2S heater voltage supply and HO2S heater low control circuits for more than 1 ohm of resistance. If the circuits test normal, replace the ECM. |
Repair Instructions
| • | Control Module References for control module replacement, setup, and programming |
Repair Verification
- Clear the DTCs with a scan tool.
- Turn OFF the ignition for 30 seconds.
- Start the engine.
- Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
| ⇒ | If this DTC resets, repeat this procedure. |
| ⇒ | If this DTC does not reset but others do, perform those diagnostics. |
