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Old 11-08-2009, 05:39 PM   #1
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Default P0418

P0418

Description
Secondary Air Injection (AIR) Pump Relay Control Circuit.

Ignition voltage is supplied directly to the secondary AIR injection pump relay. The PCM controls the relay by grounding the control circuit via and internal solid state device called a driver. The primary function of the driver is to supply the ground for the component being controlled. Each driver has a fault lint which is monitored by the PCM. When the PCM is commanding a component on, the voltage of the control circuit should be near 0 volts. When the PCM is commanding the control circuit to a component off, the voltage potential of the circuit should be near battery voltage. If the fault detection circuit senses a voltage other than what is expected, this DTC will set.
Symptoms
  • The PCM will illuminate the malfunction indicator lamp (MIL) on the second consecutive ignition cycle, which the diagnostics test has been run and failed.
  • The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails; the PCM stored the information in the Failure records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating condition at the time of the failure. The PCM write the conditions to the Freeze Frame and updated the Failure records.
Causes
  • A Short to ground, an open circuit, or short to battery voltage is detected on the control circuit.
  • The condition is present for at lest 30 seconds.

Solutions
  • From this point forward, 13 separate tests are required to isolate the DTC from a vacuum or AIR pump problem associated with the relays, command modules and feed circuits.
  • Check feed fuses and replace. If fuse fails again, a diagnostic via a TECH II is recommended.
  • Solutions may include replacing the AIR relay, repairing wiring to the control or feed circuits or replacing a faulty PCM.
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