DTC P0102 – Mass or Volume Air Flow (MAF) Circuit Low Input.

🔧 DTC P0102 – MAF Circuit Low Input

This code means the ECM is detecting a lower-than-expected voltage signal from the MAF sensor.
Common on petrol and diesel engines.

✅ Common Symptoms

Low engine power / lack of acceleration

Rough idle or stalling

Poor fuel economy

Hard starting

Black smoke (diesel)

MIL ON

🔍 Most Common Causes

1. MAF sensor dirty / contaminated

Dust, oil from air filters, crankcase vapors.

2. MAF sensor faulty

Internal failure → weak signal.

3. Wiring issues

Open in signal wire

Short to ground

Loose connector pins

Corroded terminals

4. Intake air leaks

Pipe leak between air filter → turbo → throttle

Cracked air duct

Unmetered air entering system

5. Clogged air filter

Restricts airflow → low MAF reading.

6. Low battery voltage / ECM ground issues

🧰 Step-by-Step Diagnostic Procedure

1. Visual Inspection (Always first)

Check MAF connector for damage or corrosion

Check wiring harness for cuts or rubbing

Inspect intake hoses for cracks, loose clamps

Ensure air filter is clean and properly installed

Check for aftermarket oiled filters (can contaminate the MAF)

2. Scan Tool Data

Look at MAF g/s (petrol) or kg/hr (diesel).

Typical idle readings:

Petrol: 2–7 g/s

Diesel: 6–12 g/s

If the reading is 0, 0.1, or too low, suspect:

Open signal wire

Sensor unplugged

Sensor dead

If reading is low but not zero → check intake leaks.

3. Check Power & Ground
Use a multimeter:

MAF 5-pin common wiring:

Pin 1: 12V supply (some use 5V)

Pin 2: Ground

Pin 3: MAF signal

Pin 4: IAT signal

Pin 5: 5V reference

Expected values:

Supply voltage: 12V (or 5V depending on system)

Ground: Less than 0.1V drop

Signal at idle: 0.7–1.5V (hot wire type)

If supply or ground is missing → repair wiring.

4. Check MAF Signal Wire

Backprobe signal wire

At idle: should show stable voltage

Rev to 2500 rpm: voltage should rise smoothly

If the voltage stays very low or flat, sensor faulty.

5. Check for Intake Air Leaks

Spray carb cleaner around intake duct joints

If rpm changes → leak found
Diesel engines: check intercooler pipes.

6. Clean the MAF (If reading low)

Use MAF sensor cleaner only.
Do NOT use:

Carb cleaner

Brake cleaner

Thinner

Allow to dry 15 minutes.

If readings remain low → replace the sensor.

7. ECM issues (Rare)

Only after confirming power, ground, and signal integrity.

🛠️ Recommendations

Fix order (most effective):

1. Inspect wiring + connectors

2. Check air filter + intake piping

3. Clean MAF

4. Test signal voltage

5. Replace MAF if readings stay low

6. Clear codes and perform road test

Welcome To Madurai Car Service 💐🙏🏻.