Circuit Description
Ignition voltage is supplied directly to the secondary air injection (AIR) vacuum control solenoid. The powertrain control module (PCM) controls the AIR solenoid by grounding the control circuit via an 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 line which is monitored by the PCM. When the PCM is commanding a component on, the voltage of the control circuit should be low (near 0 volts). When the PCM is commanding the control circuit to a component off, the voltage potential of the circuit should be high (near battery voltage). If the fault detection circuit senses a voltage other than what is expected, the diagnostic trouble code (DTC) P0412 will set.
The PCM will monitor the control circuit for the following:
| • | A short to ground |
| • | A short to voltage |
| • | An open circuit |
| • | An open solenoid |
| • | An internally shorted or excessively low resistance solenoid. |
When the PCM detects any of the above malfunctions, this DTC will set and the affected driver will be disabled.
Conditions for Running the DTC
| • | The ignition voltage is between 9-18 volts. |
| • | The engine speed is more than 80 RPM. |
| • | The PCM driver transitions from ON to OFF or from OFF to ON. |
Conditions for Setting the DTC
| • | A short to ground, an open circuit, or a short to battery voltage is detected on the control circuit. |
| • | The condition is present for at least 30 seconds. |
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
Diagnostic Aids
If the condition is intermittent, refer to Intermittent Conditions .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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The Diagnostic System Check-Engine Controls prompts you to complete some basic checks and store the Freeze Frame/Failure Records on the scan tool.
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Listen for an audible click when the solenoid operates. Command both the ON and OFF states. Repeat the commands as necessary.
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Tests for voltage at the feed side of the solenoid.
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Verifies that the PCM is providing ground to the solenoid.
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Tests if ground is constantly being applied to the solenoid.
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The PCM utilizes electrically erasable programmable read only memory (EEPROM). If the PCM is replaced, the new PCM must be programmed.
Step | Action | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | |||||||||
Did you perform the Diagnostic System Check-Engine Controls? | Go to Step 2 | ||||||||
Does the AIR solenoid turn ON and OFF with each command? | Go to Diagnostic Aids | Go to Step 3 | |||||||
Does the test lamp illuminate? | Go to Step 4 | Go to Step 10 | |||||||
Does the test lamp turn ON and OFF with each command? | Go to Step 8 | Go to Step 5 | |||||||
Does the test lamp remain illuminated with each command? | Go to Step 7 | Go to Step 6 | |||||||
6 |
Did you find and correct the condition? | Go to Step 13 | Go to Step 9 | ||||||
7 | Test the control circuit of the solenoid for a short to ground. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 9 | ||||||
8 | Inspect for poor connections at the AIR solenoid. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 11 | ||||||
9 | Inspect for poor connections at the powertrain control module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 12 | ||||||
10 |
Important: Check fuses. If blown, replace. Test for a short to ground or open in the coil feed circuit. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 11 | ||||||
11 | Replace the AIR solenoid. Did you complete the replacement? | Go to Step 13 | -- | ||||||
Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | Go to Step 13 | -- | |||||||
13 |
Does the DTC reset? | Go to Step 2 | Go to Step 14 | ||||||
14 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | System OK | |||||||
