P1188

Code

LAND ROVER P — Powertrain

Circuit heater resistance failure of the oxygen sensor heated (banks 1 and 2 sensor 1)

Brand: LAND ROVER

Type: P — Powertrain

Views: UK: 21 EN: 49 RU: 23

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Page language: EN

Causes

Open or high-resistance heater element in one or both upstream O2 sensors (Bank 1 and/or Bank 2 Sensor 1)
Corroded, damaged, or disconnected sensor connector(s)
Broken, shorted, or high-resistance wiring in the heater circuit (including pins, splices, terminals)
Blown fuse or faulty relay supplying heater circuit
Poor or missing ground for the heater circuit
Water ingress or contamination at sensor connector or sensor

Symptoms

Malfunction Indicator Lamp (MIL) / Check Engine Light illuminated
Reduced fuel economy and altered fuel trim due to delayed sensor warm-up
Longer cold-start emissions warm-up, possible failed emissions test
Possible rough idle or drivability symptoms if sensors stay cold
Stored P1188 (and possibly related O2 heater DTCs) in engine control module

What to check

Use a scan tool to read all stored codes and freeze frame; note if codes are stored for both banks
Monitor live data: O2 sensor heater status/duty cycle, upstream O2 voltage, fuel trims and readiness monitors
Visually inspect sensor connectors and wiring for corrosion, damage, pin push-out, or water contamination
Check relevant fuse(s) and relays for the heater circuit
With ignition off, disconnect sensor connector and measure heater element resistance at the sensor (compare to manufacturer spec)
Backprobe connector with key on and heater commanded on to check for battery voltage on supply and proper switching to ground by the ECM

Signal parameters

Heater element resistance (ohms) — measured at sensor when disconnected
Heater supply voltage (V) — battery voltage present when commanded on
Heater current (A) or inferred current draw when commanded on
Heater duty cycle or ON-time (%) reported by scan tool when commanded
Upstream O2 sensor voltage (V) and warm-up time (time to switch)
Fuel trim values (short-term and long-term) to assess sensor effect

Diagnostic algorithm

Safety first: allow exhaust and engine components to cool, secure vehicle, use personal protective equipment
Connect a capable scan tool; read and record codes, freeze-frame and live data. Clear codes and re-run to confirm P1188 returns
Visually inspect both upstream (Bank 1 and Bank 2 Sensor 1) sensor connectors, wiring harness, and grounding points for corrosion, damage or water ingress
Check relevant fuses and relays for the O2 heater circuit; replace if blown/defective
With ignition off, disconnect upstream O2 sensor(s) and measure heater resistance at the sensor connector. Compare to manufacturer specification — very high or open indicates bad heater
If resistance is out of spec at the sensor, replace the affected O2 sensor(s). If resistance is normal, continue testing wiring
With connector disconnected, backprobe supply and control wires. With key ON and heater commanded ON (use scan tool to force if available), verify battery voltage on supply and switching/ground on control circuit
Perform continuity and resistance checks from sensor connector to ECM connector to detect opens, shorts to ground/power, or high resistance. Repair any wiring faults or poor splices
If wiring and sensor measure OK but code persists, swap the upstream sensors (if identical and accessible) to see if code follows sensor or stays with circuit/ECM
If after replacing sensor(s) and repairing harness the fault remains, suspect ECM heater driver failure and refer to manufacturer procedures for ECM testing/replacement
Clear codes and road-test; verify heater operation, O2 sensor warm-up and that the code does not return

Likely causes

Failed heater element in one upstream O2 sensor
Corrosion or poor connection at sensor connector or harness splice
Open or short in the heater supply or ground wiring
Blown fuse or failed relay feeding the heater circuit
ECM driver fault (less common)

Fault status

⚠️ Status

Heater circuit resistance out of range for heated oxygen sensors Bank 1 and Bank 2 Sensor 1. ECM detected abnormal heater circuit resistance (open/short/high). MIL illuminated.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5 - 2.0 hours

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P1188 — Circuit heater resistance failure of the oxygen sensor heated (banks 1 and 2 sensor 1)