P1126

What it means

On Toyota, P1126 means the engine control unit has detected a fault in the magnetic clutch circuit, which is the air conditioning compressor clutch control. The ECU commands the clutch to engage and disengage and monitors the circuit, and it set the code because the electrical state did not match what was expected, such as an open circuit, short or unexpected voltage. Exact circuit layout and whether the clutch is switched by the ECU directly or via a relay depends on the model and engine.

Symptoms

• Air conditioning blows warm or does not get cold
• Compressor clutch does not engage, or engages intermittently
• Air conditioning clutch clicks on and off repeatedly
• Air conditioning light or climate control behaving oddly
• Engine warning light on
• Slight idle fluctuation when the air conditioning is switched on

Possible causes

• Open or short circuit in the compressor clutch wiring or connector (corrosion, chafing, loose pin)likely
• Faulty compressor magnetic clutch coil (open or shorted winding)likely
• Faulty air conditioning clutch relay or its socketpossible
• Blown fuse in the clutch or air conditioning supplypossible
• Low refrigerant charge or pressure switch fault causing the clutch to cycle or be cut outpossible
• Fault in the engine ECU or air conditioning amplifier output driverrare

How to diagnose

1. Read stored codes and freeze frame data, noting whether the air conditioning was on and any other related codes
2. Check the relevant fuses and the clutch relay for condition and correct operation
3. Visually inspect the compressor clutch connector and wiring for damage, corrosion, heat marks or chafing
4. Switch the air conditioning on and listen and watch for the clutch engaging; check for battery voltage at the clutch connector when commanded
5. Measure the clutch coil resistance and compare with the manufacturer specification for that model
6. Check wiring continuity and for shorts to earth or supply between the ECU or relay and the clutch
7. Check refrigerant pressure and the pressure switch signal, following the model-specific procedure
8. Check the clutch air gap and for a seized compressor if the coil tests good

How to fix

• Repair or replace damaged wiring and clean or replace corroded connectors
• Replace the compressor clutch coil or clutch assembly if it is out of specification
• Replace a faulty relay or blown fuse, and find out why the fuse failed
• Correct the refrigerant charge and repair any leaks, replacing a faulty pressure switch if needed
• Replace the compressor if it is seized or drawing excessive current
• Diagnose and replace the control unit only after wiring, relay and clutch are proven good

Can I keep driving?

This code for other makes

• P1126LexusMagnetic Clutch Circuit Malfunction
• P1126MazdaThrottle Position Narrow Range Sensor Circuit
• P1126NissanThermostat Function
• P1126OtherThrottle Position (Narrow Range) Sensor Circuit Malfunction
• P1126VolkswagenLong Term Fuel Trim Add Air Bank 2 System Too Lean

Nearby codes

• P1125ToyotaThrottle Control Motor Circuit
• P1127ToyotaETCS Actuator Power Source Circuit