P1646

Code

LAND ROVER P — Powertrain

Heated oxygen sensor control module, bank 1 open / in short

Brand: LAND ROVER

Type: P — Powertrain

Views: UK: 18 EN: 42 RU: 18

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Failed heated oxygen sensor (heater element open or shorted)
Damaged or chafed wiring in heater circuit (open, short to ground, short to battery)
Corroded or loose sensor connector or pin damage
Blown fuse or failed relay supplying heater circuit
Poor or missing ground at sensor or ECU connector
ECM/PCM output driver fault or internal module failure

Symptoms

Malfunction Indicator Lamp (MIL) illuminated
Possible rough idle or poor drivability if sensor not reaching operating temperature
Reduced fuel economy or increased emissions
Failed emissions test or readiness monitors not setting
Diagnostic trouble codes related to O2 sensor heaters present

What to check

Read and record freeze frame and all related DTCs using a scan tool
Visually inspect bank 1 oxygen sensor(s), connector(s) and wiring for damage, corrosion, or water ingress
Check for blown fuses and relay(s) supplying O2 sensor heater circuits
Backprobe sensor connector and measure heater supply voltage with key ON (engine OFF)
Measure heater element resistance at the sensor with connector unplugged
Perform a wiggle test on harness/connectors while monitoring for code or voltage change

Signal parameters

Heater resistance (typical range): ~2–15 Ω depending on sensor design — consult OEM spec for exact value
Supply voltage at heater circuit: battery voltage (~11–14 V) when heater fuse/relay powered (key ON)
ECM switching: heater often driven by ECM ground-side switching or pulse-width modulation; expected control waveform when active (scan tool or scope)
Current draw: typically up to a few amps when heater energized (sensor-specific)

Diagnostic algorithm

Connect a capable scan tool, confirm P1646 and note any related codes and freeze frame data
Perform a visual inspection of bank 1 O2 sensor(s), connector and wiring harness for corrosion, damage or pin push-out
With ignition OFF, unplug the O2 sensor connector and measure heater element resistance across the heater pins; compare to OEM spec (very high/infinite = open)
Check continuity from the sensor heater pins to the ECM connector pins; look for open circuit or short to ground/battery
With key ON (engine OFF), backprobe the supply pin at the sensor connector to verify battery voltage is present (if circuit is fused/switched)
With key ON and heater enabled (use manufacturer test or scan tool command if available), check for ECM control signal (switching to ground or PWM) and measure voltage/current. Use a lab scope if necessary to detect shorts or driver faults
If wiring, connector, and fuse/relay are good but heater resistance is out of spec, replace the oxygen sensor(s) on bank 1
If a new sensor does not clear the fault and wiring/fuse/relay are verified good, suspect ECM driver fault and consider module testing/replacement per OEM procedures
After repairs, clear codes and perform a drive/functional test to ensure code does not return and readiness monitors set

Likely causes

Heater element in bank 1 oxygen sensor failed (high resistance or open)
Connector corrosion at the sensor causing intermittent open/short
Wire rubbed through and shorting to chassis ground after flexing/harness contact
Blown heater fuse or failed relay supplying the heater circuit
ECM pin or driver transistor failed (less common)

Fault status

⚠️ Status

Heated oxygen sensor control module detected an open or short in the bank 1 sensor heater circuit; ECM has set a fault and illuminated MIL.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5 - 2.5 hours

Repair manuals

Manual library for LAND ROVER

413

Browse 413 LAND ROVER manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

LAND ROVER

Your experience will help others

+100 karma for a short comment :)

Was this AI description helpful?

Your feedback helps improve AI descriptions.

👍 Like 0 👎 Dislike 0

Send to email

P1646 — Heated oxygen sensor control module, bank 1 open / in short