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Home / DTC / P1031 — Heated Oxygen Sensor (HO2S) Heater Current Monitor Control Circuit Banks 1 and 2 Sensor 1

P1031 — Heated Oxygen Sensor (HO2S) Heater Current Monitor Control Circuit Banks 1 and 2 Sensor 1

Detailed page for trouble code P1031.

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P1031

HUMMER P — Powertrain

Heated Oxygen Sensor (HO2S) Heater Current Monitor Control Circuit Banks 1 and 2 Sensor 1

Brand: HUMMER
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Open or short in HO2S heater wiring harness for Bank 1 and/or Bank 2 Sensor 1
  • Failed oxygen sensor heater element (one or both sensors)
  • Blown fuse or failed heater relay supplying sensor heaters
  • Corroded or loose connector at sensor or ground
  • PCM/ECM fault or internal driver failure
  • Aftermarket or incorrect replacement sensor with wrong heater characteristics

Symptoms

  • Malfunction indicator lamp (MIL/CEL) illuminated
  • Longer cold start warm-up and rougher cold idle
  • Reduced fuel economy and increased emissions
  • Possible failed emissions test
  • Diagnostic trouble codes related to O2 sensors or fuel trim

What to check

  • Read freeze frame and live data to confirm code and related codes
  • Visual inspection of sensor connectors, wiring harness and grounds for damage or corrosion
  • Check fuse(s) and heater relay that supply upstream oxygen sensor heaters
  • Measure heater element resistance at each Bank1 S1 and Bank2 S1 sensor (with sensor disconnected)
  • Back-probe heater supply and control circuit to measure voltage/current during key on/engine run
  • Perform continuity and short-to-ground/power checks between sensors and PCM connector pins

Signal parameters

  • Typical HO2S heater resistance (ambient): commonly ~2–20 ohms depending on sensor design — refer to vehicle service manual for exact spec
  • Heater current draw when energized: commonly ~0.3–1.5 A (varies by sensor); refer to service data
  • Heater supply voltage: battery voltage (~12 V) when relay/power present; control/pwm from PCM may switch/ground
  • No continuity (infinite ohms) indicates open heater element; very low resistance (~

Diagnostic algorithm

  1. Retrieve all stored DTCs and freeze frame data; note whether both banks set the code simultaneously and any related codes (heater, fuel trim, PCM).
  2. Perform a visual inspection of both Bank 1 and Bank 2 Sensor 1 connectors and wiring for heat damage, chafing, corrosion or rodent damage.
  3. Check relevant fuses and the heater relay (if fitted). Replace blown fuses and retest.
  4. With ignition ON (engine off), back-probe the sensor heater power supply pin(s) to confirm presence of fused battery voltage or relay-supplied voltage. If no supply, trace to fuse/relay.
  5. With sensor disconnected, measure heater element resistance for B1S1 and B2S1. Compare to service spec. Infinite = open heater; extremely low = short.
  6. If resistance is within spec, reconnect sensors and with engine running (or with PCM commanding heater on), measure current draw using an inline ammeter or clamp meter on the heater feed. Compare to expected range.
  7. Check for short-to-ground or short-to-power on heater control circuits and check continuity to PCM. Wiggle harness while monitoring data to detect intermittent faults.
  8. If wiring and power/grounds are good but heater element is out of spec on one or both sensors, replace the faulty sensor(s).
  9. If wiring/power/grounds and sensors test good, investigate PCM heater driver output; consider repair or replacement of PCM only after confirming harness and sensors.
  10. Clear codes and perform road test to verify repair. Re-scan to confirm no reoccurrence.

Likely causes

  • Common power/ground feed (fuse or relay) feeding both B1S1 and B2S1 has failed
  • Wiring short to ground or to battery between PCM and both sensor heaters
  • Both sensor heater elements have degraded (less likely than wiring or fuse)
  • Connector corrosion at front O2 sensor harness (exposed to heat/road debris)

Fault status

⚠️ Status
HO2S heater current monitor/control circuit fault detected for Banks 1 & 2 Sensor 1 — abnormal heater current (open/short/low/high) or supply/driver issue.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

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