DTC P0103 – Mass or Volume Air Flow (MAF) Circuit High Input.

🚗 DTC P0103 – MAF CIRCUIT HIGH INPUT (P010300)

This code means the MAF sensor signal voltage to the ECM is higher than the expected range.
The ECM interprets this as too much air flow, usually caused by sensor/voltage issues—not actual airflow.

✅ COMMON SYMPTOMS

Hard starting / long crank

Rough idle

Poor fuel economy

Black smoke (rich mixture)

Reduced power

MIL ON

🎯 MAIN POSSIBLE CAUSES

1. MAF Sensor Faulty

Internal short

Contaminated sensor element (oil, dirt, dust)

2. Wiring / Connector Faults

Signal wire shorted to power (5V or 12V)

Poor ground

Corroded connector

Damaged harness near air intake

3. Air Intake System Issues

Air leaks between air filter → MAF → throttle body

Aftermarket/oiled air filters contaminating sensor

4. Power Supply Issues

Incorrect 5V reference from ECM

ECM internal fault (rare)

🔧 DIAGNOSTIC STEPS (WORKSHOP GUIDE)

STEP 1 — Visual Inspection

Check:

Air filter box properly closed

MAF sensor orientation correct

No debris, no oil contamination

All hose clamps tight (no air leaks)

If contaminated → Clean using MAF cleaner only (NO carb/brake cleaner).

STEP 2 — Scanner Live Data Check

Look at MAF g/s at idle:

Normal idle values:

Petrol: 2–7 g/s

Diesel: 6–12 g/s

If MAF shows too high (example: 20–50 g/s at idle)
→ Electrical fault or sensor fault.

STEP 3 — Check Power Supply & Ground

Using multimeter:

Pin voltage expectations (common 3–5 pin MAF):

5V reference: 4.8–5.1V

Ground: < 0.1V drop

Signal wire at idle: 0.7–1.5V (varies by vehicle)

If signal > 4–5V at idle → High circuit input (P0103)

Likely causes:

Signal wire shorted to 5V

Sensor internal short

STEP 4 — Wiggle Test

While engine idles:

Wiggle MAF harness

Watch live data
If reading spikes → harness fault.

STEP 5 — Check for Unmetered Air Leaks

Look for:

Cracks in intake boot

Loose clamps

Vacuum leaks after MAF

If unmetered air enters → ECM sees high airflow.

STEP 6 — Substitute a Known Good MAF Sensor

If wiring & intake OK →
Replace MAF sensor (most common fix)

⭐ COMMON FIXES

1. Clean MAF sensor

2. Repair wiring/connector

3. Replace faulty MAF sensor

4. Fix intake pipe leaks

5. Replace clogged/incorrect air filter

🛑 IMPORTANT SPECIAL NOTES

Never use oiled air filters → they contaminate MAF

If MAF is aftermarket cheap brand → HIGH FAILURE RATE

Some diesels require MAF calibration after replacement

Welcome To Madurai Car Service 💐🙏.