Code
P0051
Generic
P — Powertrain
HO2S Heater Control Circuit Low Bank 2 Sensor 1
Views:
UK: 26
EN: 46
RU: 28
AI status
Completed
Completed
100%
Causes
- Open or high-resistance heater element in the Bank 2 Sensor 1 oxygen sensor
- Short to ground or damaged wiring in the heater circuit
- Corroded or loose connector at the sensor or harness
- Blown fuse or failed relay supplying the sensor heater
- Faulty PCM driver (less common)
Symptoms
- Check engine light (MIL) illuminated
- Possible increased fuel consumption or rough idle if closed-loop control is affected
- Failed emissions test (higher tailpipe emissions)
- Possible stored and/or pending related fuel-trim or oxygen-sensor codes
What to check
- Scan for P0051 and any other related codes (P0052, P0031, P0135, etc.) and view freeze frame/live data
- Visually inspect sensor connector and wiring for corrosion, heat damage, chafing, or broken wires
- Verify relevant fuse(s) and heater relay are present and functional
- Back-probe harness to measure heater supply voltage and control signal while key ON/engine running per service manual
- Measure heater element resistance at the sensor (compare to spec) and check for short to ground or open circuit
Signal parameters
- Heater element typical resistance: roughly 2–20 ohms (manufacturer-specific — consult manual)
- Heater supply voltage: approximately battery/ignition voltage (near 12 V) on the supply pin with key ON
- PCM control side: circuit may be switched to ground by PCM; when active that pin may measure near 0 V
- When heater is commanded ON, expect significant current draw (hundreds of mA to a few amps) — check with clamp meter if needed
- Open-circuit indicated by very high/OL resistance; short-to-ground indicated by near-zero resistance or low supply voltage
Diagnostic algorithm
- Capture freeze-frame and live data. Note any other O2 heater or oxygen sensor codes and battery voltage.
- Perform a visual inspection of the Bank 2 Sensor 1 connector, wiring harness, and nearby components for damage or corrosion.
- Check fuses and heater-related relay(s). Replace if blown or faulty.
- With connector disconnected, measure heater element resistance across the sensor heater pins. Compare to vehicle specification. Replace sensor if resistance is out of spec or open.
- Check for shorts: measure resistance from sensor heater pins to chassis ground and to battery positive to identify short to ground or short to supply.
- Reconnect harness and back-probe: with ignition ON (or engine running if required by service manual), verify heater supply voltage on the supply pin and monitor control pin while commanding the heater ON with a scan tool. Control pin should show PCM switching behavior (to ground or to voltage as specified).
- Wiggle test wiring while watching live data/voltage for intermittent faults. Repair or replace damaged wiring or connector.
- If wiring and sensor test good but circuit still reports low, inspect PCM driver output for correct operation. Consider swapping with known-good sensor (or bench test) before replacing PCM.
- Clear codes and perform a drive cycle to confirm repair. Re-scan for recurrence.
Likely causes
- Failed oxygen sensor heater (most common)
- Damaged wiring or connector (chafing, corrosion, broken wire)
- Blown fuse or bad relay supplying heater power
- PCM output driver fault (least common)
Fault status
Status
P0051 — HO2S Heater Control Circuit Low (Bank 2, Sensor 1). The powertrain control module detected a low-voltage or low-current condition in the heater circuit for the upstream oxygen sensor on bank 2. This may be caused by an open/heating element failure, wiring/connector fault, blown fuse/relay, or a PCM driver issue.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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Code
P0051
HUMMER
P — Powertrain
Heated Oxygen Sensor (HO2S) Heater Circuit Low Voltage Bank 2 Sensor 1
Views:
UK: 21
EN: 32
RU: 22
AI status
Completed
Completed
100%
Causes
- Open or high-resistance heater element in the Bank 2 Sensor 1 oxygen sensor
- Short to ground or damaged wiring in the heater circuit
- Corroded or loose connector at the sensor or harness
- Blown fuse or failed relay supplying the sensor heater
- Faulty PCM driver (less common)
Symptoms
- Check engine light (MIL) illuminated
- Possible increased fuel consumption or rough idle if closed-loop control is affected
- Failed emissions test (higher tailpipe emissions)
- Possible stored and/or pending related fuel-trim or oxygen-sensor codes
What to check
- Scan for P0051 and any other related codes (P0052, P0031, P0135, etc.) and view freeze frame/live data
- Visually inspect sensor connector and wiring for corrosion, heat damage, chafing, or broken wires
- Verify relevant fuse(s) and heater relay are present and functional
- Back-probe harness to measure heater supply voltage and control signal while key ON/engine running per service manual
- Measure heater element resistance at the sensor (compare to spec) and check for short to ground or open circuit
Signal parameters
- Heater element typical resistance: roughly 2–20 ohms (manufacturer-specific — consult manual)
- Heater supply voltage: approximately battery/ignition voltage (near 12 V) on the supply pin with key ON
- PCM control side: circuit may be switched to ground by PCM; when active that pin may measure near 0 V
- When heater is commanded ON, expect significant current draw (hundreds of mA to a few amps) — check with clamp meter if needed
- Open-circuit indicated by very high/OL resistance; short-to-ground indicated by near-zero resistance or low supply voltage
Diagnostic algorithm
- Capture freeze-frame and live data. Note any other O2 heater or oxygen sensor codes and battery voltage.
- Perform a visual inspection of the Bank 2 Sensor 1 connector, wiring harness, and nearby components for damage or corrosion.
- Check fuses and heater-related relay(s). Replace if blown or faulty.
- With connector disconnected, measure heater element resistance across the sensor heater pins. Compare to vehicle specification. Replace sensor if resistance is out of spec or open.
- Check for shorts: measure resistance from sensor heater pins to chassis ground and to battery positive to identify short to ground or short to supply.
- Reconnect harness and back-probe: with ignition ON (or engine running if required by service manual), verify heater supply voltage on the supply pin and monitor control pin while commanding the heater ON with a scan tool. Control pin should show PCM switching behavior (to ground or to voltage as specified).
- Wiggle test wiring while watching live data/voltage for intermittent faults. Repair or replace damaged wiring or connector.
- If wiring and sensor test good but circuit still reports low, inspect PCM driver output for correct operation. Consider swapping with known-good sensor (or bench test) before replacing PCM.
- Clear codes and perform a drive cycle to confirm repair. Re-scan for recurrence.
Likely causes
- Failed oxygen sensor heater (most common)
- Damaged wiring or connector (chafing, corrosion, broken wire)
- Blown fuse or bad relay supplying heater power
- PCM output driver fault (least common)
Fault status
Status
P0051 — HO2S Heater Control Circuit Low (Bank 2, Sensor 1). The powertrain control module detected a low-voltage or low-current condition in the heater circuit for the upstream oxygen sensor on bank 2. This may be caused by an open/heating element failure, wiring/connector fault, blown fuse/relay, or a PCM driver issue.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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Code
P0051
LAND ROVER
P — Powertrain
Heated Oxygen Sensor Heater Control Circuit Low (bank 2 sensor 1)
Views:
UK: 14
EN: 26
RU: 14
AI status
Completed
Completed
100%
Causes
- Open or high-resistance heater element in the Bank 2 Sensor 1 oxygen sensor
- Short to ground or damaged wiring in the heater circuit
- Corroded or loose connector at the sensor or harness
- Blown fuse or failed relay supplying the sensor heater
- Faulty PCM driver (less common)
Symptoms
- Check engine light (MIL) illuminated
- Possible increased fuel consumption or rough idle if closed-loop control is affected
- Failed emissions test (higher tailpipe emissions)
- Possible stored and/or pending related fuel-trim or oxygen-sensor codes
What to check
- Scan for P0051 and any other related codes (P0052, P0031, P0135, etc.) and view freeze frame/live data
- Visually inspect sensor connector and wiring for corrosion, heat damage, chafing, or broken wires
- Verify relevant fuse(s) and heater relay are present and functional
- Back-probe harness to measure heater supply voltage and control signal while key ON/engine running per service manual
- Measure heater element resistance at the sensor (compare to spec) and check for short to ground or open circuit
Signal parameters
- Heater element typical resistance: roughly 2–20 ohms (manufacturer-specific — consult manual)
- Heater supply voltage: approximately battery/ignition voltage (near 12 V) on the supply pin with key ON
- PCM control side: circuit may be switched to ground by PCM; when active that pin may measure near 0 V
- When heater is commanded ON, expect significant current draw (hundreds of mA to a few amps) — check with clamp meter if needed
- Open-circuit indicated by very high/OL resistance; short-to-ground indicated by near-zero resistance or low supply voltage
Diagnostic algorithm
- Capture freeze-frame and live data. Note any other O2 heater or oxygen sensor codes and battery voltage.
- Perform a visual inspection of the Bank 2 Sensor 1 connector, wiring harness, and nearby components for damage or corrosion.
- Check fuses and heater-related relay(s). Replace if blown or faulty.
- With connector disconnected, measure heater element resistance across the sensor heater pins. Compare to vehicle specification. Replace sensor if resistance is out of spec or open.
- Check for shorts: measure resistance from sensor heater pins to chassis ground and to battery positive to identify short to ground or short to supply.
- Reconnect harness and back-probe: with ignition ON (or engine running if required by service manual), verify heater supply voltage on the supply pin and monitor control pin while commanding the heater ON with a scan tool. Control pin should show PCM switching behavior (to ground or to voltage as specified).
- Wiggle test wiring while watching live data/voltage for intermittent faults. Repair or replace damaged wiring or connector.
- If wiring and sensor test good but circuit still reports low, inspect PCM driver output for correct operation. Consider swapping with known-good sensor (or bench test) before replacing PCM.
- Clear codes and perform a drive cycle to confirm repair. Re-scan for recurrence.
Likely causes
- Failed oxygen sensor heater (most common)
- Damaged wiring or connector (chafing, corrosion, broken wire)
- Blown fuse or bad relay supplying heater power
- PCM output driver fault (least common)
Fault status
Status
P0051 — HO2S Heater Control Circuit Low (Bank 2, Sensor 1). The powertrain control module detected a low-voltage or low-current condition in the heater circuit for the upstream oxygen sensor on bank 2. This may be caused by an open/heating element failure, wiring/connector fault, blown fuse/relay, or a PCM driver issue.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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Code
P0051
MITSUBISHI
P — Powertrain
Oxygen sensor heater2(front)low
Views:
UK: 20
EN: 28
RU: 19
AI status
Completed
Completed
100%
Causes
- Open or high-resistance heater element in the Bank 2 Sensor 1 oxygen sensor
- Short to ground or damaged wiring in the heater circuit
- Corroded or loose connector at the sensor or harness
- Blown fuse or failed relay supplying the sensor heater
- Faulty PCM driver (less common)
Symptoms
- Check engine light (MIL) illuminated
- Possible increased fuel consumption or rough idle if closed-loop control is affected
- Failed emissions test (higher tailpipe emissions)
- Possible stored and/or pending related fuel-trim or oxygen-sensor codes
What to check
- Scan for P0051 and any other related codes (P0052, P0031, P0135, etc.) and view freeze frame/live data
- Visually inspect sensor connector and wiring for corrosion, heat damage, chafing, or broken wires
- Verify relevant fuse(s) and heater relay are present and functional
- Back-probe harness to measure heater supply voltage and control signal while key ON/engine running per service manual
- Measure heater element resistance at the sensor (compare to spec) and check for short to ground or open circuit
Signal parameters
- Heater element typical resistance: roughly 2–20 ohms (manufacturer-specific — consult manual)
- Heater supply voltage: approximately battery/ignition voltage (near 12 V) on the supply pin with key ON
- PCM control side: circuit may be switched to ground by PCM; when active that pin may measure near 0 V
- When heater is commanded ON, expect significant current draw (hundreds of mA to a few amps) — check with clamp meter if needed
- Open-circuit indicated by very high/OL resistance; short-to-ground indicated by near-zero resistance or low supply voltage
Diagnostic algorithm
- Capture freeze-frame and live data. Note any other O2 heater or oxygen sensor codes and battery voltage.
- Perform a visual inspection of the Bank 2 Sensor 1 connector, wiring harness, and nearby components for damage or corrosion.
- Check fuses and heater-related relay(s). Replace if blown or faulty.
- With connector disconnected, measure heater element resistance across the sensor heater pins. Compare to vehicle specification. Replace sensor if resistance is out of spec or open.
- Check for shorts: measure resistance from sensor heater pins to chassis ground and to battery positive to identify short to ground or short to supply.
- Reconnect harness and back-probe: with ignition ON (or engine running if required by service manual), verify heater supply voltage on the supply pin and monitor control pin while commanding the heater ON with a scan tool. Control pin should show PCM switching behavior (to ground or to voltage as specified).
- Wiggle test wiring while watching live data/voltage for intermittent faults. Repair or replace damaged wiring or connector.
- If wiring and sensor test good but circuit still reports low, inspect PCM driver output for correct operation. Consider swapping with known-good sensor (or bench test) before replacing PCM.
- Clear codes and perform a drive cycle to confirm repair. Re-scan for recurrence.
Likely causes
- Failed oxygen sensor heater (most common)
- Damaged wiring or connector (chafing, corrosion, broken wire)
- Blown fuse or bad relay supplying heater power
- PCM output driver fault (least common)
Fault status
Status
P0051 — HO2S Heater Control Circuit Low (Bank 2, Sensor 1). The powertrain control module detected a low-voltage or low-current condition in the heater circuit for the upstream oxygen sensor on bank 2. This may be caused by an open/heating element failure, wiring/connector fault, blown fuse/relay, or a PCM driver issue.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
Similar codes
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