P0031, ho25circuit low, bank 1 sensor 1. sft b1 -3.91, ltft b1 .78, stft b2 -3.91, ltft b2 3.91. R&R ox sensor or what
Hello,
P0031 - Bank 1 Heated Oxygen Sensor No. 1 Heater Circuit - Low Voltage. That is what this code means.
DTC P0031 is set when Bank 1 HO2S No.1 heater current is less then .09 amps, or potential difference between heater positive and negative terminals is more then 13.99 volts while HO2S heater is on. MIL (The engine light) is illuminated when Engine Control Module (ECM) detects malfunction during 2 consecutive drive cycles.
Possible Causes are:
- Bank 1 HO2S No. 1 heater circuit malfunction
- Bank 1 HO2S No. 1 heater malfunction
- ECM malfunction
- HO2S heater relay
DTC Confirmation Test (Advanced/Intermediate Users): Ensure intake air tempature is 18f (-8c) or more, engine coolant tempature is 18-230f (-8-110c) and vehicle is at an altitude of 8000 feet or below, and barometric pressure is 75 kPa or more. Turn ignition off, connect scan tool and turn ignotion on. Using scan tool, clear DTCs. Start engine and run at idle speed for 5 minutes. Using scan tool check for current or pending DTC P0031.
Diagnosis & Repair Procedure (Advanced/Intermediate Users):
1. If engine system check has been performed, go to the next step. If engine system check has not been performed, do the system check.
2. Turn ignition off. Disconnect Bank 1 HO2S No. 1 4-pin harness connector. Bank 1 HO2S No. 1 is located in the left exhause pipe before catalytic convertor. Measure resistance between Bank 1 HO2S No. 1 pigtail connector terminal No. 3 (Green wire) and No. 4 (Blue wire). Resistance should be 5.0-6.4 ohms at 68f (20c). If resistance is as specified, go to next step. If resistence is not as specified, replace HO2S. After repair repeat DTC Confirmation Test (Above).
3. Disconnect HO2S heater relay. HO2S heater relay is located on the left fender well. Turn ignition On. Measure voltage between ground and HO2S heater relay socket cavity No. 3 (Black/White wire). Also measure voltage between ground and HO2S heater relay socket cavity No. 1 (Blue/White wire). If voltage readings at both measurements is 10-14 voltes, go to step 5. If voltage readings are not as specified go to next step.
4. Check for blown HO2S (15-amp) or IG COIL (20-amp) fuses. Fufses are located in the underhood fuse and relay boxc. If fuses are okay, check for open or short it to ground in Black/White wire between IG COIL fuse HO2S heater relay. If problem is found repair as necessary. After repair repeat DTC Confirmation Test (Above).
5. Turn Ignition off. Install HO2S heater relay. Dicsonnect ECM 30-pin harness connector C51-2. ECM is located under instrument panel, under glove box. Measure voltage between ground and ECM harness connector C51-2 terminal No. 4 (Green wire). If voltage reading is 10-14 volts, subsitute a known-good ECM, and repeat DTC Confirmation Test (Above). If DTC does not reset, testing is complete. If voltage readings are not specified, go to next step.
6. Check for short to ground in Green wire between Bank 1 HO2S No. 1 and ECM. If no problem with wiring is found, replace HO2S heater relay. If problem persists after repairs, subsitute a known-good ECM and repeat DTC Confirmation Test (Above).
I hope this helps and is what your looking for. Best of luck.
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