P1500

Alternator FR Terminal Circuit

Car Fault Codes Mitsubishi Engine computer & electrical

Can you still drive? Yes, normally

Who can fix it? Needs a workshop

Typical repair time 30 minutes – 2.5 hours

Typical cost SAR 100 to 2,000

What it means

This is a Mitsubishi-specific code; the same number can mean something different on other makes. The alternator's FR terminal sends the engine computer a signal showing how much electrical load the alternator is carrying, so the computer can compensate idle speed when loads switch on. The code means the computer detected an open circuit or an invalid signal in this circuit.

Models covered: Mitsubishi models, mainly around 1996–2006 (e.g. Lancer, Galant, Pajero/Montero).

Symptoms4

Check engine light on.
Idle speed dips or the engine shakes when the A/C, lights or fans switch on.
Often no other symptoms if charging is normal.
The battery light may come on if the alternator itself is faulty.

Possible causes5

A loose or corroded connector at the alternator.
A broken or shorted wire between the FR terminal and the ECM.
A faulty voltage regulator inside the alternator.
A faulty alternator.
A faulty ECM (rare).

How to diagnose4

Measure battery and charging voltage with the engine running to confirm the alternator charges normally.
Inspect the alternator connector and wiring for corrosion or damage, especially near hot parts.
Check FR wire continuity between the alternator and the ECM, and make sure it is not shorted to ground or power.
Watch the FR signal as electrical loads are switched on and off, and compare with the manufacturer specification.

How to fix5

Clean and reseat the alternator connector.
Repair the broken or shorted FR wire.
Replace the voltage regulator or alternator if the signal is not coming out of it correctly.
Check the ECM if the signal and wiring are good.
Clear the codes and watch the idle with electrical loads switched on.

Repair cost

0–500

500–2,000

2,000–5,000

5,000+

In Saudi riyals; the highlighted part is the expected range for this fault.

The cost is low when a connector or wire is the cause, and rises if a voltage regulator or new alternator is needed.

Prices are rough estimates for common cars at independent workshops and vary with the car and the source of the part.
Prices last updated: September 2026

Frequently asked questions

Does this code mean the alternator is not charging?

Not necessarily. The code concerns the load signal the alternator sends to the computer, and charging may still be fine. Measure charging voltage to confirm.

Why does the engine shake when the A/C is on with this code?

The computer uses the FR signal to raise idle slightly when electrical load increases; without it, compensation can lag and the idle dips.

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This guide is for information only and does not replace an inspection by a qualified technician. If the fault involves brakes, steering, engine temperature, electrics or refrigerant, do not attempt the repair yourself.

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