Circuit Description
A secondary air injection (AIR) pump is used on this vehicle to lower tailpipe emissions on start-up. The VCM supplies a ground to the AIR pump relay control circuit. This energizes the AIR pump relay and supplies voltage to the AIR pump clutch. The VCM uses the HO2S voltages and the short term fuel trim to diagnose the secondary air injection system.
The VCM monitors the HO2S voltages and the short term fuel trim value when the AIR pump is energized. This additional air causes the HO2S voltages to shift low, reflecting the leaner mixture. The short term fuel trim should increase above 128 confirming that the VCM is supplying additional fuel. The low HO2S voltages and higher short term fuel trim value provide confirmation that the secondary air injection system is operating properly. When the AIR pump is de-energized, the HO2S voltages should increase and begin switching normally.
If only one HO2S responded as expected, the VCM sets either a DTC P1415 or P1416 depending on which engine bank the AIR system is inoperative.
Conditions for Running the DTC
| • | No active ECT DTCs |
| • | No active IAC DTCs |
| • | No active HO2S DTCs |
| • | No active misfire DTCs |
| • | No active MAP sensor DTCs |
| • | No active fuel trim DTCs |
| • | No active EVAP DTCs |
| • | No active TP sensor DTCs |
| • | No active IAT DTCs |
| • | No active MAF DTCs |
| • | The system voltage is greater than 10 volts |
| • | The IAT is greater than 0°C (32°F) |
| • | The power enrichment mode is not active |
| • | Decel fuel cut-off not active |
| • | The commanded air/fuel ratio is 14.7:1 |
| • | The engine speed is greater than 550 RPM |
| • | The engine load is less than 50% |
| • | The MAF is less than 100 g/s |
| • | The ECT is between 75°C and 105°C (167°F to 221°F) |
| • | The system has been in closed loop mode for more than 15 seconds |
Conditions for Setting the DTC
The VCM has not detected a change in HO2S voltage and short term fuel trim when the secondary air injection pump is energized.
Action Taken When the DTC Sets
The VCM will turn ON the malfunction indicator lamp (MIL) after two consecutive test cycles with the fault active.
Conditions for Clearing the MIL or DTC
| • | The control module turns OFF the MIL after 3 consecutive drive trips when the test has run and passed. |
| • | A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles. A warm-up cycle occurs when the coolant temperature has risen 22°C (40°F) from the startup coolant temperature and the engine coolant reaches a temperature that is more than 70°C (158°F) during the same ignition cycle. |
| • | Use a scan tool in order to clear the DTCs. |
Diagnostic Aids
Intermiitent conditions can be cause by wiring problems.
An intermittent may be caused by any of the following conditions:
| • | A poor connection |
| • | Rubbed through wire insulation |
| • | A broken wire inside the insulation |
Thoroughly check any circuitry that is suspected of causing the intermittent complaint. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.
If a repair is necessary, refer to Wiring Repairs or Connector Repairs in Wiring Systems.
Test Description
Number(s) below refer to the step number(s) on the diagnostic table.
-
This step determines if the cause of the DTC is still present.
-
This step determines if there is a problem before or after the check valve.
Step | Action | Value(s) | Yes | No | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 |
Important: Before clearing DTC(s) use the scan tool to record Freeze Frame and Failure Records for reference, as data will be lost when the Clear Info function is used. Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | |||||||||||
Does the Short Term Fuel Trim Bank 1 indicate a change of more than the specified value within 30 seconds? | 16 % | Go to Step 3 | Go to Step 4 | |||||||||||
3 | The DTC is intermittent. Are any additional DTCs stored? | -- | Go to the applicable DTC table | Go to Diagnostic Aids | ||||||||||
4 | Check the AIR System Bank 1 for the following:
Did you find a problem? | -- | Go to Step 8 | Go to Step 5 | ||||||||||
Does air flow from the hose? | -- | Go to Step 6 | Go to Step 7 | |||||||||||
6 | Check for restrictions or leaks in the check valve and the AIR pipe on Bank 1. Did you find a problem? | -- | Go to Step 8 | Go to Diagnostic Aids | ||||||||||
7 | Check for restrictions or leaks in the Bank 1 AIR hose between the AIR shut off valve and the check valve. Did you find a problem? | -- | Go to Step 8 | |||||||||||
8 | Repair as necessary. Refer to Secondary Air Injection Check Valve and Check Valve Pipe Replacement . Is the action complete? | -- | Go to Step 9 | -- | ||||||||||
9 |
Does the scan tool indicate that this diagnostic Ran and Passed? | -- | Go to Step 10 | Go to Step 2 | ||||||||||
10 | Using the scan tool, select Capture Info, Review Info. Are any additional DTCs displayed that have not been diagnosed? | -- | Go to the applicable DTC table | System OK |
