What is the difference between P0100 and P0101?

P0101 means the sensor is sending a signal, but the value does not match what the engine computer expects for the engine speed and load, which usually points to a dirty sensor or an air leak. P0100 means the circuit itself has failed: no signal, no supply or a signal outside the electrical range. That shifts the diagnosis toward connectors, wires, fuses and the sensor's electronics.

Can I drive with P0100?

Only gently and only as far as the workshop. Many diesels and turbocharged petrols go into limp mode with capped power, which is unsafe when overtaking or merging. Naturally aspirated petrol engines usually keep running on a substitute value but can hesitate and stall at junctions. It is not a code to ignore for weeks.

Will cleaning the MAF sensor fix P0100?

Sometimes, but less often than for P0101. Cleaning helps when the sensing element is so fouled that its output has collapsed. Most P0100 faults are electrical, such as a loose or corroded plug, a broken wire or a blown fuse, so check the connector and supply before spending money. Always use a dedicated MAF cleaner and never touch the element.

Why does my diesel lose power with P0100?

A diesel uses the MAF reading to control exhaust gas recirculation and to limit fuel against the air actually available. Without a trustworthy reading, the engine computer usually caps fuel and boost to protect the engine and avoid heavy smoke, which you feel as limp mode. Power returns once the circuit is repaired and the code is cleared.

How much does it cost to fix P0100?

Cleaning and reseating a loose or corroded connector can cost nothing if you do it yourself, or up to about €50 at a workshop. A wiring repair typically runs €70 to €240, most of it fault-finding time. A replacement MAF sensor costs about €70 to €230 fitted for an aftermarket part and €110 to €380 for an original-equipment one.

P0100: Mass or Volume Air Flow Circuit Malfunction

Quick Answer

Safe to drive (short-term)

P0100 means the engine computer has lost a usable signal from the mass air flow (MAF) sensor circuit, the sensor in the intake that measures how much air the engine draws in. Unlike P0101, where the sensor works but reads implausibly, P0100 points at the circuit itself: missing power or ground, a broken or shorted signal wire, a corroded plug or a dead sensor. The engine switches to a backup airflow estimate, so it runs less smoothly, uses more fuel and, on many diesels, loses power.

Severity: Moderate · Fuel System

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What does P0100 mean?

P0100 is a fuel system-related diagnostic trouble code classified as moderate severity. When your vehicle's ECU detects this condition, it stores P0100 and illuminates the check engine light.

Where it is on the car

Air filter box
Mass airflow sensor (MAF)
Throttle body and throttle position sensor
Intake manifold and MAP sensor
Engine (cylinder head)

What are the symptoms of P0100?

If your vehicle has triggered P0100, you may notice one or more of these symptoms:

Check engine light on, sometimes with a reduced power warning
Reduced power or limp mode, common on diesels and turbocharged petrol engines
Hesitation or stumble when accelerating
Rough idle or stalling, especially when coming to a stop
Higher fuel consumption
Black smoke under acceleration on some diesels
Longer cranking before the engine starts on some engines

What causes P0100?

Here are the most common causes of P0100:

Unplugged, loose or corroded MAF sensor connector
: high
Broken or chafed wire in the MAF harness, including the power feed and ground, not only the signal wire
: high
Failed MAF sensor electronics giving no output
: medium
Blown fuse or failed relay supplying the MAF sensor
: medium
Sensing element so heavily fouled by oil mist or an over-oiled air filter that the output collapses
: low
Engine computer input fault, only after the wiring has been proven good
: low

Is it safe to drive with P0100?

Generally yes, for short-term driving. Many diesels and turbocharged petrol engines cut power (limp mode) as soon as they lose the airflow signal, because the engine computer also uses it for EGR and boost control, and a sudden loss of power makes overtaking or joining fast traffic unsafe. A naturally aspirated petrol engine usually keeps running on a substitute value, but it can hesitate, idle roughly or stall at junctions. Drive gently and directly to a workshop rather than living with the code.

How do you diagnose P0100?

Follow these steps to pinpoint the root cause of P0100:

Read every stored code. P0100 together with other sensor or supply-voltage codes points to a shared power feed, relay or ground rather than the MAF sensor itself
Read the live MAF value (the standard OBD2 airflow reading, in grams per second) with the engine idling. A warm four-cylinder petrol typically shows roughly 2 to 7 g/s. A value stuck at zero, or pinned at an impossible maximum, while the engine runs points to the circuit fault. On some cars the reading shows the engine computer's substitute value while the code is active, so a plausible number does not clear the circuit on its own
Inspect the MAF connector: look for a broken locking tab, green corrosion, water in the plug or pushed-back pins. Wiggle the harness while watching the live value; a reading that jumps as you move it is a wiring fault
Backprobe the connector with the key on. Check for supply voltage (battery voltage on many hot-film sensors, a 5 V reference on some), a good ground (within about 0.1 V of battery negative), and a signal that changes when the engine runs
If the supply is missing, check the fuse and relay that feed the sensor, then the wire between them and the plug
If supply and ground are good but there is no signal, check the signal wire for continuity to the engine computer. If the wire is intact, replace the MAF sensor
Clear the code and test drive with some firm acceleration. On a diesel, confirm that full power has returned and the code does not come back

How much does P0100 cost to fix?

Repair costs for P0100 vary depending on the root cause and your vehicle. Here are typical estimates:

Repair	Parts Cost	Labor Cost	Total Estimate	DIY Difficulty
Clean, reseat and secure the MAF sensor connector	€0–€10	€0–€40	€0–€50	Easy
Replace blown fuse or failed supply relay	€1–€40	€0–€40	€1–€80	Easy
Repair MAF sensor wiring (power feed, ground or signal) or connector pins	€10–€60	€60–€180	€70–€240	Moderate
Replace MAF sensor (aftermarket)	€40–€150	€30–€80	€70–€230	Easy
Replace MAF sensor (OEM)	€80–€300	€30–€80	€110–€380	Easy

Prices estimated as of March 2026. Costs vary by region, vehicle, and shop.

Full repair guides

Mass Airflow Sensor (MAF) Cost

P0100 on specific vehicles

P0100 behaves differently depending on your vehicle. Select your car below for model-specific causes and known issues:

P0100 on Volkswagen

Volkswagen Golf

See Volkswagen-specific causes & cost

P0100 on Toyota

Toyota RAV4 2.4 (2AZ-FE)

See Toyota-specific causes & cost

These codes are often seen alongside P0100 or indicate related issues:

Common questions about P0100

What does P0100 mean?: P0100 means the engine computer has detected a fault in the electrical circuit of the mass air flow (MAF) sensor, so it no longer has a usable reading of how much air the engine is drawing in. Because fuelling, and on diesels EGR and boost control, depend on that reading, the engine switches to a substitute value and usually runs worse until the fault is fixed.
What is the difference between P0100 and P0101?: P0101 means the sensor is sending a signal, but the value does not match what the engine computer expects for the engine speed and load, which usually points to a dirty sensor or an air leak. P0100 means the circuit itself has failed: no signal, no supply or a signal outside the electrical range. That shifts the diagnosis toward connectors, wires, fuses and the sensor's electronics.
Can I drive with P0100?: Only gently and only as far as the workshop. Many diesels and turbocharged petrols go into limp mode with capped power, which is unsafe when overtaking or merging. Naturally aspirated petrol engines usually keep running on a substitute value but can hesitate and stall at junctions. It is not a code to ignore for weeks.
Will cleaning the MAF sensor fix P0100?: Sometimes, but less often than for P0101. Cleaning helps when the sensing element is so fouled that its output has collapsed. Most P0100 faults are electrical, such as a loose or corroded plug, a broken wire or a blown fuse, so check the connector and supply before spending money. Always use a dedicated MAF cleaner and never touch the element.
Why does my diesel lose power with P0100?: A diesel uses the MAF reading to control exhaust gas recirculation and to limit fuel against the air actually available. Without a trustworthy reading, the engine computer usually caps fuel and boost to protect the engine and avoid heavy smoke, which you feel as limp mode. Power returns once the circuit is repaired and the code is cleared.
How much does it cost to fix P0100?: Cleaning and reseating a loose or corroded connector can cost nothing if you do it yourself, or up to about €50 at a workshop. A wiring repair typically runs €70 to €240, most of it fault-finding time. A replacement MAF sensor costs about €70 to €230 fitted for an aftermarket part and €110 to €380 for an original-equipment one.

Read our detailed guides

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