P0418
DTC P0412 or P0418
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptor
DTC P0412
- Secondary Air Injection (AIR) Solenoid Control Circuit
DTC P0418
- Secondary Air Injection (AIR) Pump Control Circuit
Diagnostic Fault Information
Circuit/System Description
The secondary air injection (AIR) system aids in the reduction of hydrocarbon emissions during a cold start. The electric air pump forces fresh air into the exhaust stream in order to accelerate the catalyst operation. Ignition voltage is supplied directly to the secondary air injection pump relay and secondary air solenoid valve relay. The Engine Control Module (ECM) controls the relays by grounding the control circuit with a solid state device called a driver. The ECM monitors the the control circuits for open, short to ground, or shorted to a voltage condition.
Conditions for Running the DTC
* The ignition is ON, or the engine is operating.
* The ignition voltage is between 9-18 V.
* The ECM has commanded the air system ON and OFF at least once during the ignition cycle.
* The DTCs run continuously once the above conditions are met.
Conditions for Setting the DTC
The ECM detects that the commanded state of the driver and the actual state of the control circuit do not match for greater than 2 seconds.
Action Taken When the DTC Sets
DTC P0412, and P0418 are Type B DTCs.
Conditions for Clearing the DTC
DTC P0412, and P0418 are Type B DTCs.
Diagnostic Aids
If the condition is intermittent, move the related harnesses and connectors, with the engine operating, while monitoring the circuit status for the component with a scan tool. The circuit status parameter changes from OK or Not Run to Fault if there is a condition with the circuit or a connection.
Reference Information
Schematic Reference
Engine Controls Schematics [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views Connector End Views By Name
Description and Operation
Secondary Air Injection System Description Description and Operation
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References Programming and Relearning for scan tool information
Circuit/System Verification
1. Ignition ON, command the appropriate relay ON and OFF with a scan tool. You should hear an audible click or the Secondary Air component should turn ON and OFF.
2. Command the appropriate relay ON and OFF with a scan tool while observing the relay control circuit status parameters. Each parameter should display OK or Not Run.
3. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Circuit/System Testing
1. Ignition OFF, remove the appropriate relay.
2. Ignition ON, verify that a test lamp illuminates between the relay coil B+ circuit terminal 85 and ground.
• If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition circuit fuse is open, test all components connected to the ignition circuit and replace as necessary.
3. Verify a test lamp does not illuminate between the relay control circuit terminal 86 and B+.
• If the test lamp illuminates, test the control circuit for a short to ground. If the circuit tests normal, replace the ECM.
4. Test for less than 1 V between the relay coil control circuit terminal 86 and ground.
• If greater than the specified range, test the control circuit for a short to voltage. If the circuit tests normal, replace the ECM.
5. Connect a DMM set to the diode setting between the control circuit terminal 86 and ground.
6. Command the appropriate relay ON and OFF with a scan tool. The DMM should transition from 2.5-3.5 V when commanded OFF to less than 1 V when commanded ON.
• If the circuit voltage does not correspond to the specified values, test the control circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
7. If all circuits test normal, test or replace the appropriate relay.
Component Testing
1. Ignition OFF, disconnect the appropriate relay.
2. Test for the following resistance between terminals 85 and 86.
* 50-75 ohm-Secondary Air Injection Pump Relay
* 70-110 ohm-Secondary Air Injection Solenoid Relay
• If the resistance is not within the specified range, replace the relay.
3. Test for infinite resistance between the following terminals:
* 86 and 87
* 86 and 30
* 85 and 87
* 87 and 30
• If not the specified value, replace the relay.
4. Install a 15 A fused jumper wire between relay terminal 86 and B+. Install a jumper wire between relay terminal 85 and ground. Test for less than 2 ohm between terminals 87 and 30.
• If greater than the specified range, replace the relay.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Relay Replacement (Attached to Wire Harness) Relay Replacement (Attached to Wire Harness)Relay Replacement (Within an Electrical Center) Relay Replacement (Within an Electrical Center)
* Control Module References Programming and Relearning for Engine Control Module replacement, setup, and programming