Code Definition

P1135 — Ignition Switch Signal Missing or Improper

System: Powertrain  |  Type: Manufacturer-Specific  |  Make: Ford

About P1135

P1135 is a manufacturer-specific powertrain diagnostic trouble code recorded for Ford vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

P1135 is a manufacturer-specific code. The same code string on a different make may have a different meaning. Always confirm the code's definition against the vehicle's service information for the specific make and model under test.

Code Information

This DTC sets when the Powertrain Control Module (PCM) does not receive a valid or consistent ignition switch signal, which it needs for proper powertrain control. The ignition switch signal tells the PCM the key position such as RUN and START and lets it coordinate fuel delivery, emissions readiness, and sensor activation. A missing, intermittent, or improper signal disrupts system initialisation and can prevent normal operation. The driver may notice an illuminated check engine light, a hard or no start, stalling, or accessories behaving inconsistently with key position.

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