P1490 — 13 documented meanings by make

P1490 does not mean the same thing on every car — manufacturers reuse the number for different faults. 14 makes document it: Audi, Chrysler, Citroen, Ford, Mazda, Mercedes-Benz, Mitsubishi, Nissan, Opel / Vauxhall, Peugeot, SEAT, Skoda, Subaru, Volkswagen. Find your make below.

P1490 on Audi, SEAT, Skoda, Volkswagen

On Audi, SEAT, Skoda, Volkswagen vehicles P1490 is documented as: Activated charcoal filter system solenoid 2, N333, short circuit to ground. P1490 is stored when the ECU sees short to ground on the circuit named in the code. That describes how the circuit is behaving, not which part has failed — the wiring, the connector and the component itself can all produce it, which is why the checks below start with the cheapest.

Usually one of: Wiring insulation chafed through where the loom passes a bracket or edge; Water or salt in a connector bridging the signal pin to the body; The component itself shorted internally; A harness pinched during earlier repair work.

Check first, cheapest first:

1. Unplug the component and re-read the code — if it changes, the fault is in the component, not the wiring
2. Inspect the loom where it passes metal edges, brackets and hinges
3. Open the connector and check for green corrosion or moisture
4. Measure resistance from the signal pin to a body ground; near-zero confirms the short
5. Repair the harness section, or replace the component if it shorted internally

Related Audi, SEAT, Skoda, Volkswagen codes:

P1490 on Chrysler

On Chrysler vehicles P1490 is documented as: Low speed fan control relay circuit. P1490 is stored when the ECU sees signal too low on the circuit named in the code. That describes how the circuit is behaving, not which part has failed — the wiring, the connector and the component itself can all produce it, which is why the checks below start with the cheapest.

Usually one of: High resistance in the supply or ground path, dragging the signal down; Corroded connector adding resistance the module reads as a low reading; Sensor drifted out of tolerance with age; Partial short to ground somewhere in the signal line.

Check first, cheapest first:

1. Read the live value on a scanner and compare with a known-good reading
2. Clean and re-seat the connector, then re-test before replacing anything
3. Check the ground point for that circuit — a poor ground causes this far more often than a bad sensor
4. Measure the sensor against specification with the connector back-probed
5. Replace the sensor only once the wiring and ground have been ruled out

Related Chrysler codes:

P1490 on Citroen, Mazda, Peugeot

On Citroen, Mazda, Peugeot vehicles P1490 is documented as: Secondary air relief solenoid circuit. P1490 points at secondary air injection. The standard definition names the system involved; which part inside it has actually failed is what the checks below establish, cheapest first.

Related Citroen, Mazda, Peugeot codes:

P1490 on Ford

On Ford vehicles P1490 is documented as: Evaporative emission system vacuum cut/bypass solenoid circuit. P1490 points at evaporative emissions system. The standard definition names the system involved; which part inside it has actually failed is what the checks below establish, cheapest first.

Usually one of: Fuel cap not sealing or the wrong cap fitted; Cracked or perished breather hose; Purge valve stuck open; Charcoal canister split; Leaking tank seal around the pump flange.

Check first, cheapest first:

1. Refit the fuel cap firmly, clear the code and drive for a few days — a surprising share of these are the cap
2. Inspect the visible EVAP hoses for cracks and loose clamps
3. Command the purge valve with a scanner and listen for it clicking
4. Smoke-test the system if the simple checks find nothing — a small leak is very hard to see

Related Ford codes:

P1490 on Mercedes-Benz

On Mercedes-Benz vehicles P1490 is documented as: Evaporative emission system purge control valve circuit. P1490 points at evaporative emissions system. The standard definition names the system involved; which part inside it has actually failed is what the checks below establish, cheapest first.

Usually one of: Fuel cap not sealing or the wrong cap fitted; Cracked or perished breather hose; Purge valve stuck open; Charcoal canister split; Leaking tank seal around the pump flange.

Check first, cheapest first:

1. Refit the fuel cap firmly, clear the code and drive for a few days — a surprising share of these are the cap
2. Inspect the visible EVAP hoses for cracks and loose clamps
3. Command the purge valve with a scanner and listen for it clicking
4. Smoke-test the system if the simple checks find nothing — a small leak is very hard to see

Related Mercedes-Benz codes:

P1490 on Mitsubishi

On Mitsubishi vehicles P1490 is documented as: Low speed fan control relay fault. P1490 is stored when the ECU sees signal too low on the circuit named in the code. That describes how the circuit is behaving, not which part has failed — the wiring, the connector and the component itself can all produce it, which is why the checks below start with the cheapest.

Usually one of: High resistance in the supply or ground path, dragging the signal down; Corroded connector adding resistance the module reads as a low reading; Sensor drifted out of tolerance with age; Partial short to ground somewhere in the signal line.

Check first, cheapest first:

1. Read the live value on a scanner and compare with a known-good reading
2. Clean and re-seat the connector, then re-test before replacing anything
3. Check the ground point for that circuit — a poor ground causes this far more often than a bad sensor
4. Measure the sensor against specification with the connector back-probed
5. Replace the sensor only once the wiring and ground have been ruled out

Related Mitsubishi codes:

P1490 on Nissan

On Nissan vehicles P1490 is documented as: Vacuum cut/bypass valve.

Related Nissan codes:

P1490 on Opel / Vauxhall

On Opel / Vauxhall vehicles P1490 is documented as: Additional coolant pump, open circuit; Additional cooling pump relay, open circuit; Additional coolant pump circuit, high/low voltage; Additional cooling pump relay, short circuit to ground; Additional cooling pump relay, short circuit to battery. P1490 is stored when the ECU sees open circuit on the circuit named in the code. That describes how the circuit is behaving, not which part has failed — the wiring, the connector and the component itself can all produce it, which is why the checks below start with the cheapest.

Usually one of: Broken wire, most often at a flex point such as a door hinge or engine mount; Corroded or pushed-back terminal in the connector; Blown fuse on the supply side; Component failed with an internally open winding or element.

Check first, cheapest first:

1. Check the relevant fuse first — it is the cheapest thing that produces this code
2. Unplug and inspect both halves of the connector for corrosion and terminal fit
3. Continuity-test the wire end to end while flexing the loom by hand
4. Measure the component itself against its specification
5. Repair the break or replace the component, whichever the measurement points to

Related Opel / Vauxhall codes:

P1490 on Subaru

On Subaru vehicles P1490 is documented as: Thermostat malfunction. P1490 is stored when the ECU sees malfunction on cooling system. That describes how the circuit is behaving, not which part has failed — the wiring, the connector and the component itself can all produce it, which is why the checks below start with the cheapest.

Usually one of: Wiring or connector fault in the circuit; Component failed electrically; Supply or ground problem feeding the circuit; Controlling module fault, though this is the least common of the four.

Check first, cheapest first:

1. Read all stored codes — a general fault code is often the symptom of a more specific one
2. Inspect the connector and wiring for the named component
3. Check supply and ground at the component
4. Measure the component against specification
5. Replace the component once wiring and supply are ruled out

Related Subaru codes:

Which one is yours

A generic OBD reader gives you the number, not which of these meanings your manufacturer assigned to it. To get to the specific one:

1. Use a brand-specific scanner — VCDS for VAG, INPA or ISTA for BMW, XENTRY for Mercedes, Forscan for Ford. It shows the manufacturer's own text rather than the generic one.
2. Read all stored codes together — the neighbouring ones usually point at which system is involved and narrow the list.
3. Check freeze-frame data: the RPM, temperature and load at the moment it triggered indicate which system was active.
4. If you have no brand scanner, tell me the make and model below and I will tell you which of these applies to your car.

Code family

P1xxx is manufacturer-specific code (VW/Audi, BMW, Mercedes, Toyota etc. have different meanings for the same code number).

Severity

Manufacturer-specific codes need a brand scanner (VCDS for VAG, INPA for BMW, STAR for Mercedes).

That is what holds for P1490 in general. From here it depends on your engine — tell me which car it is and what it does, and I will give you the steps for it: real procedures, torque figures and diagrams instead of general advice.