DTC P0100 – Mass or Volume Air Flow (MAF) Circuit Malfunction.
Use this as you would a service-manual flowchart.

🔧 DTC P0100 – MAF Circuit Malfunction

This code means the ECM has detected an electrical or signal fault in the MAF sensor circuit.
It is NOT always the sensor itself—wiring, intake leaks, or power issues often cause it.

1. Common Symptoms

Hard starting

Rough idle

Low power / hesitation

Poor fuel economy

Black smoke or rich running

MIL ON (Check Engine)

2. Possible Causes

MAF Sensor / Air Intake Related

Dirty or failed MAF sensor

Wrong type of sensor installed (aftermarket non-OEM)

Air leaks between air filter → MAF → throttle body

Clogged or oily aftermarket air filter

PCV hose leaks

Electrical / Wiring

Open/short in MAF signal wire

Open/short in 5V reference

Open/short in ground circuit

Poor connection at sensor or ECM pin

Corroded connectors (common in humid regions)

Other Related Causes

Low battery voltage

Intake backfire damaging the sensor

Incorrect installation after service

3. Pinout Reference (Typical 5-Wire Hot-Film MAF)

Pin Function

1 5V reference or ignition 12V
2 Ground
3 MAF Signal (0.5–4.5 V)
4 IAT Signal (if integrated)
5 IAT Ground

(Note: Exact pinout may vary by vehicle—verify with manufacturer.)

4. Step-By-Step Diagnostic Procedure

Step 1: Visual Inspection

🌟 Check air intake piping for cracks / loose clamps
🌟 Check air filter condition
🌟 Ensure MAF is clean and oriented correctly (arrow toward engine)
🌟 Inspect connector for corrosion / water intrusion
🌟 Confirm correct sensor fitted (no universal MAF)

Step 2: Check MAF Sensor Power & Ground

Use a multimeter.

Power Supply

Ignition ON

You should see 12V (or 5V, depending on design).
If missing → inspect fuse, relay, power distribution.

Ground Check

Perform voltage drop test (<0.1 V drop recommended).
If poor ground → repair ground point / wiring.

Step 3: Check Signal Wire Output

Backprobe MAF signal wire.

Typical values (engine idling):

0.8–1.2 V (petrol)

1.0–1.5 V (diesel)

Increase RPM slowly:

Voltage should rise smoothly

No dropouts or sudden spikes

If signal flat or erratic → faulty MAF or wiring fault.

Step 4: Check for Intake Air Leaks

Use:

Smoke machine

Brake cleaner spray (around intake, observe idle change)

Leaks after MAF will cause incorrect readings and trigger P0100.

Step 5: Scan Tool Data Analysis

Check:

MAF g/s at Idle

Petrol: 2–7 g/s

Diesel: 6–12 g/s

MAF g/s at 2500 rpm (no load)

Petrol: 8–15 g/s

Diesel: 15–25 g/s

If reading is too low or stuck → sensor fault or air leak.

Step 6: Wiring Continuity Test

Unplug MAF and ECM, then measure:

Signal wire continuity to ECM

5V line continuity

Check for shorts to ground or 12V

If wiring OK → sensor likely defective.

Step 7: Sensor Cleaning (If Dirty)

If hot wires have dust/oil:

Use MAF Cleaner Spray ONLY

Do NOT touch hot wire

Do NOT use carb cleaner/throttle spray

If still faulty after cleaning → replace sensor.

5. When to Replace the MAF Sensor

Replace if:

Signal voltage is erratic

Sensor does not respond to airflow increase

No communication on signal line despite good power/ground

Internal damage or contamination

Use OEM or high-quality brand—cheap sensors often cause repeat codes.

6. After Repair

Clear codes

Perform a short test drive

Check live data → MAF values should be stable

Ensure long-term fuel trims return to normal

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