Explanation of Code P1124 on 2002 Nissan Altima: “Throttle Control Motor Relay Stuck”
Severity
- Level : 🔴 High (risk of loss of throttle control or engine stalling).
- Urgency :
- Throttle stuck in open/closed position → Immediate danger.
- Limp mode activated (reduced power).
Common Symptoms
- 🚨 Check engine light on (MIL).
- 🛑 Unresponsive throttle or erratic response.
- 🐌 Loss of power or unstable engine RPM.
Main Causes
- Faulty throttle control motor relay :
- Stuck contacts (stuck ON/OFF) or faulty coil.
- Wiring issues :
- Short circuit or open circuit in the relay harness.
- Corrosion at the relay or ECM connector.
- ECM failure (rare) :
- Relay control error (software or internal circuit).
Diagnostic Procedure (Detailed Steps)
Step 1: Relay Location
- Where? : Relay box under the hood (refer to user manual).
- Identification : Look for relay labeled “Throttle Control Motor Relay”.
Step 2: Relay Testing
- Tools : Multimeter, 12V battery (to activate relay).
- Procedure :
- Unplug relay and measure coil resistance (expected value: 50-120 Ω).
- Test contacts :
- Without power : No continuity between terminals 30 and 87.
- With 12V on coil : Continuity between 30 and 87.
Step 3: Electrical Circuit Inspection
- Power supply : Check 12V at terminal 30 (red/yellow wire) with ignition ON.
- ECM control : Measure voltage at terminal 85 (green/black wire) → Should be 0V with ignition OFF, 12V with ignition ON.
Step 4: ECM Connector Check
- Location : ECM box (under dashboard on passenger side).
- Action : Inspect pins C109-45 and C109-46 for corrosion or damage.
Solutions & Costs
| Problem | Solution | Average Cost |
|---|---|---|
| Faulty relay | Replacement (new relay) | €20 – €50 |
| Wiring repair | Harness/connector repair | €50 – €150 |
| ECM connector cleaning | Contact spray + dielectric grease | €10 – €30 |
| ECM reprogramming | At Nissan dealership | €100 – €300 |
Mistakes to Avoid
- ❌ Forcing relay into socket : Risk of bending pins.
- ❌ Ignoring related codes (e.g., P0120, P0220) : Also check pedal sensor.
Practical Case
- Problem : Code P1124 on a 2002 Nissan Altima with stuck throttle.
- Diagnosis : Relay stuck in ON position (constant power to throttle motor).
- Solution : Relay replacement (€35) + ECM connector cleaning.
Pro Tips
- Test with identical relay : Swap with non-critical relay (e.g., headlights) for verification.
- Check throttle motor : Remove and test with direct 12V (should open/close smoothly).
If the problem persists, consult a professional equipped with Nissan Consult-II tools for in-depth analysis! 🔧🚗⚠️