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P1490

Secondary Air Relief Solenoid Circuit Malfunction.

  • Other
  • Powertrain
  • Manufacturer code
  • Low severity

How this code is built

P
SystemPowertrain
1
Defined byThe manufacturer
4
AreaAuxiliary emission controls
90
FaultThe specific fault in that area

What it means

P1490 is a manufacturer-specific code. For the make given here it means the Secondary Air Relief Solenoid Circuit Malfunction. The engine control unit monitors the electrical circuit of the solenoid that relieves or controls pressure or vacuum in the secondary air system. It set the code because the circuit voltage or current did not match what it expected when it switched the solenoid, which points to an open circuit, a short or a faulty coil. Other makes use P1490 for different faults, so confirm the definition for your exact vehicle.

Symptoms

  • Engine warning light on
  • Possible additional secondary air system codes stored
  • Failed emissions test
  • Air pump noise that is louder, absent or runs at the wrong time on a cold start
  • Usually no noticeable change in how the car drives

Possible causes

  • Damaged, chafed or corroded wiring or connector at the relief solenoidlikely
  • Solenoid coil failed internally (open circuit or short)likely
  • Blown fuse or faulty relay or power feed to the solenoid circuitpossible
  • Water or contamination in the solenoid connector causing high resistancepossible
  • Wiring short to earth or to supply between the solenoid and the control unitpossible
  • Fault in the control unit output driver for the solenoidrare

How to diagnose

  1. Read all stored and pending codes and note the freeze frame data, including whether the fault is current or intermittent
  2. Look up the solenoid location and wiring layout for the specific model and engine, as the layout varies
  3. Inspect the solenoid, its connector and the harness for damage, heat, rubbing, corrosion or water ingress
  4. Check the fuse and any relay supplying the secondary air system
  5. Measure the solenoid coil resistance and compare it with the manufacturer specification
  6. With the connector unplugged, check for supply voltage and a good earth or switched signal as the wiring diagram shows
  7. Operate the solenoid using a scan tool active test if available, and listen or feel for it clicking
  8. Check continuity of each wire to the control unit and test for shorts to earth or supply, and only then suspect the control unit

How to fix

  • Repair or replace damaged wiring and clean or renew corroded connector terminals
  • Replace the relief solenoid if its resistance or operation is out of specification
  • Replace the blown fuse or faulty relay after finding out why it failed
  • Dry out and seal the connector, and fix the source of water ingress
  • Repair or replace the control unit only if testing proves the output driver is faulty, then clear the code and confirm it does not return

Can I keep driving?

Low severity

The car can normally be driven as the fault mainly affects cold-start emissions control. Book it in soon, as the warning light will stay on and the car may fail an emissions test.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.

This code for other makes

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