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DTC codes / Jaguar codes / P1566

P1566 · JaguarSpeed Control Command Switch Out Range Low

P1566 on a Jaguar means the engine control module (ECM) has seen the speed control command switch circuit report a voltage below the expected range for the switch position selected. The ECM compares the analog voltage from the steering-wheel switch pack against a stored table and flags the code when the signal falls outside the low limit, usually because of a poor connection, a faulty switch, or a wiring fault in the column circuit.

SystemPowertrain
Code typeJaguar specific
SeverityLow
Fix difficultyIntermediate
AreaVehicle speed, idle control and auxiliary inputs

Symptoms you may notice

  • Cruise control fails to engage or drops out unexpectedly while driving
  • The cruise control indicator lamp may flash or stay off when the set button is pressed
  • Steering-wheel buttons for resume, set, or cancel feel unresponsive or require extra pressure
  • Often no symptoms besides the warning light, with cruise control still working intermittently
  • Other steering-wheel-mounted controls may behave erratically if the clock spring is involved
  • A stored code may reappear immediately after clearing if the fault is continuous

Common causes, most likely first

  1. Worn or contaminated speed control switch contacts inside the steering-wheel switch pack
  2. Damaged or chafed wiring in the steering column or clock spring (spiral cable) causing a low-voltage short
  3. Corroded or loose connector at the switch pack or at the ECM harness
  4. High resistance in the switch ground circuit, pulling the signal voltage below the expected range
  5. Faulty clock spring assembly interrupting or shorting the switch signal
  6. Internal fault in the ECM's switch input circuit (rare but possible after other causes are ruled out)

How to diagnose and fix it

  1. Scan all modules for stored and pending codes, then clear P1566 and road-test to confirm whether it returns
  2. Inspect the steering-wheel switch pack connector and the column harness for corrosion, chafing, or loose pins
  3. Measure the switch signal voltage at the ECM connector while pressing each cruise button and compare with Jaguar's specification
  4. Check the ground circuit resistance from the switch pack to the chassis and repair any high-resistance ground
  5. Test the clock spring continuity and resistance through its full steering range, replacing it if readings are inconsistent
  6. Substitute a known-good speed control switch pack and recheck the signal voltage and code status
  7. If all external circuits and components test good, perform a guided diagnostic on the ECM input circuit before considering ECM replacement

Why the switch voltage drops low

  • A common oversight is replacing the switch pack without checking the ground circuit, because a poor ground pulls the signal voltage low and mimics a failed switch.
  • The clock spring is a frequent hidden cause on older Jaguars, since internal ribbon damage can short the switch signal to ground only at certain steering angles.
  • P1566 can set intermittently from nothing more than a dirty contact in the switch pack, so a thorough cleaning and dielectric grease application often resolves it without parts.
  • Do not assume the ECM is faulty just because the code persists after clearing; the ECM input circuit is rarely the root cause and should be tested last.
  • Related codes such as P1567 (switch out of range high) or U-codes for lost communication with the steering column module may appear alongside P1566 and point to a shared wiring fault.

Can I keep driving with P1566?

The vehicle remains safe to drive because the fault affects only cruise control operation, but avoid using the speed control system until it is repaired so you are not caught by an unexpected disengagement. If the warning light is accompanied by other electrical symptoms, have the steering column circuits inspected promptly.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for Jaguar vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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