Secondary Air Injection System Diagnosis. Chevrolet Tahoe

For 1990-2009 cars only

Makes 🢒 Chevrolet 🢒 1999 🢒 Tahoe - 2WD 🢒 Engine 🢒 Engine Controls - 5.0L and 5.7L 🢒 Secondary Air Injection System Diagnosis

AIR/EVAP - Comp Loc Figure
Air Pump Controls
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

Circuit Description

A fused ignition voltage is supplied to the AIR Pump Relay. The VCM controls the AIR Pump by grounding the AIR Pump Relay Control circuit. This energizes the relay and supplies voltage to the AIR Pump and the AIR Solenoid. When the fuel system goes into Closed Loop, the VCM opens the ground to the AIR Control circuit.

Diagnostic Aids

An AIR Pump that is stuck on could cause a fuel trim lean code.

An AIR Solenoid or AIR Shut Off Valve that is stuck open could allow the exhaust system to draw air in unintentionally through the AIR System.

An AIR supply hose that is melted before the check valve could indicate exhaust gas back-flow past the check valve.

Low AIR System volume may cause a DTC P1415, P1416 or an intermittent complaint. Also check for the following conditions:

•	Pinched, kinked, or restricted AIR pipes, hoses or fittings

•	Leaks, holes, loose fittings or hoses

•	Restricted or obstructed AIR Pump inlet

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 will determine if the AIR System is functioning correctly.

This step will ensure that the VCM is capable of turning the AIR Pump OFF.

This step will determine if the VCM is capable of controlling the AIR Pump Relay.

This step is to check for a short to voltage on the control circuit.

The engine must be running for this test to ensure a vacuum supply to the system.

This step is to check for an AIR Solenoid stuck open.

This step is to ensure the AIR Shut Off Valve closes when the vacuum supply is removed.

This step will determine if the AIR Pump is capable of producing airflow.

An open fuse for the battery feed circuit could be caused by a short to ground in the components operated by the relay. Also check the wiring in the circuits on the switched side of the relay. Refer to Diagnostic Aids.

Step

Action

Value(s)

Yes

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

Go to Step 2

Go to the Powertrain On Board Diagnostic (OBD) System Check

Install the scan tool.
Start the engine and allow it to run for 2 minutes.
Verify the engine is running at normal operating temperature and is in Closed Loop.
Command ON the AIR Pump with the scan tool.

Does the Short Term Fuel Trim indicate a change of more than the specified value within 30 seconds?

16%

Go to Step 3

Go to Step 4

The condition is intermittent.

Are any DTCs stored?

Go to the applicable DTC table

Go to Diagnostic Aids

Turn ON the ignition leaving the engine OFF.
Command ON the AIR Pump with the scan tool.

Is the AIR Pump running?

Go to Step 5

Go to Step 9

Command OFF the AIR Pump.

Is the AIR Pump running?

Go to Step 6

Go to Step 20

Turn OFF the ignition.
Disconnect the AIR Pump Relay.
Turn ON the ignition leaving the engine OFF.

Is the air pump running?

Go to Step 35

Go to Step 7

Probe the AIR Pump Relay Control circuit at the relay connector with the test lamp connected to B+.

Is the test lamp ON?

Go to Step 8

Go to Step 43

Turn OFF the ignition.
Disconnect the VCM C1 connector.
Turn ON the ignition leaving the engine OFF.
Probe the AIR Pump Relay Control circuit at the relay connector with the test lamp connected to B+.

Is the test lamp ON?

Go to Step 41

Go to Step 47

Turn OFF the ignition.
Disconnect the AIR Pump connector.
Check for a poor connection at the AIR Pump. Refer to Diagnostic Aids.

Did you find a problem?

Go to Step 33

Go to Step 10

Turn ON the ignition leaving the engine OFF.
Connect a test lamp to a ground.
Probe the terminal for the AIR Pump feed circuit on the engine harness side of the AIR Pump connector.
Command ON the AIR Pump with the scan tool.

Is the test lamp ON?

Go to Step 11

Go to Step 12

Connect a test lamp to B+.
Probe the terminal for the AIR Pump ground circuit on the engine harness side of the AIR Pump connector.

Is the test lamp ON?

Go to Step 46

Go to Step 34

Turn OFF the ignition.
Disconnect the AIR Pump Relay.
Check for a poor connection at the AIR Pump Relay. Refer to Diagnostic Aids.

Did you find a problem?

Go to Step 33

Go to Step 13

Check for an open in the AIR Pump feed circuit between the AIR Relay and the AIR Pump.

Did you find a problem?

Go to Step 33

Go to Step 14

Connect a test lamp to a ground.
Probe the terminal for the battery feed circuit at the AIR Pump Relay connector.

Is the test lamp ON?

Go to Step 15

Go to Step 36

Turn ON the ignition.
Probe the terminal for the ignition feed circuit at the AIR Pump Relay connector with the test lamp to a ground.

Is the test lamp ON?

Go to Step 16

Go to Step 37

Connect a test lamp to B+.
Probe the terminal for the AIR Pump Relay Control circuit at the relay connector.
Command ON the AIR Pump with the scan tool.

Is the test lamp ON?

Go to Step 43

Go to Step 17

Turn OFF the ignition.
Disconnect the VCM C1 connector.
Check for a poor connection at the VCM. Refer to Diagnostic Aids.

Did you find a problem?

Go to Step 33

Go to Step 18

Check for an open in the AIR Pump Relay Control circuit between the relay and the VCM.

Did you find a problem?

Go to Step 33

Go to Step 19

Turn ON the ignition.
Connect a test lamp to a ground.
Probe the terminal for the AIR Pump Relay Control circuit at the relay connector.

Is the test lamp ON?

Go to Step 38

Go to Step 47

Disconnect the AIR Shut Off Valve output hose at the AIR Shut Off Valve.
Start the engine and allow it to idle.
Command ON the AIR Pump with the scan tool.

Does air flow from the AIR Shut Off Valve?

Go to Step 21

Go to Step 23

Disconnect the vacuum hose at the AIR Shut Off Valve.
Install a vacuum gauge on the AIR Shut Off Valve vacuum hose.
Command OFF the AIR Pump with the scan tool.

Is vacuum present on the hose?

Go to Step 45

Go to Step 22

Turn OFF the ignition.
Turn ON the ignition leaving the engine OFF.
Command ON the AIR pump with the scan tool.

Does air flow from the AIR Shut Off Valve?

Go to Step 44

Go to Step 30

Turn OFF the ignition.
Disconnect the AIR Pump output hose at the AIR Shut Off Valve.
Turn ON the ignition leaving the engine OFF.
Command ON the AIR pump with the scan tool.

Does air flow from the hose?

Go to Step 24

Go to Step 31

Disconnect the vacuum hose at the AIR Shut Off Valve.
Install a vacuum gauge on the AIR Shut Off Valve vacuum hose.
Start the engine and allow it to idle.
Command ON the AIR Pump with the scan tool

Is the vacuum above the specified value while the AIR Pump is running?

10 in Hg

Go to Step 44

Go to Step 25

Check for a leak or restriction in the vacuum hose between the AIR Solenoid and the AIR Shut Off Valve

Did you find a problem?

Go to Step 42

Go to Step 26

Remove the vacuum connector at the AIR Solenoid.
Install the vacuum gauge on the source hose coming from the engine.
Measure the vacuum with the engine running.

Is the vacuum above the specified value?

10 in Hg

Go to Step 27

Go to Step 32

Turn OFF the ignition.
Disconnect the AIR Solenoid harness connector.
Check for a poor connection at the AIR Solenoid. Refer to Diagnostic Aids.

Did you find a problem?

Go to Step 33

Go to Step 28

Turn ON the ignition leaving the engine OFF.
Connect a test lamp to a ground and probe the terminal for the solenoid feed circuit at the connector.
Command ON the AIR Pump with the scan tool.

Is the test lamp ON?

Go to Step 29

Go to Step 40

Turn OFF the ignition.
Connect a test lamp to B+.
Probe the terminal for the solenoid ground circuit at the connector.

Is the test lamp ON?

Go to Step 45

Go to Step 39

Check for leaks or restrictions on the following components:

•	AIR Shut Off Valve

•

Hoses

•	Check valves

•

Fittings

•

AIR pipes

•	Exhaust manifolds

Did you find a problem?

Go to Step 42

Go to Diagnostic Aids

Check for a restriction or an obstruction in the inlet hose of the AIR Pump.

Did you find a problem?

Go to Step 42

Go to Step 46

Repair the leak or restriction in the vacuum supply hose to the AIR Solenoid.

Is the action complete?

Go to Step 48

Repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

Go to Step 48

Repair the open in the AIR Pump ground circuit. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

Go to Step 48

Repair the short to voltage in the AIR Pump feed circuit. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

Go to Step 48

Repair the open or short to ground in the battery feed circuit for the AIR Pump Relay. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

Go to Step 48

Repair the open or short to ground in the ignition feed circuit to the AIR Pump Relay. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

Go to Step 48

Repair the short to voltage on the AIR Pump Relay Control circuit. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

Go to Step 48

Repair the open in the AIR Solenoid ground circuit. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

Go to Step 48

Repair the open in the AIR Solenoid feed circuit. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

Go to Step 48

Repair the short to ground in the AIR Relay Control circuit. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

Go to Step 48

Repair as necessary. Refer to Secondary Air Injection Check Valve and Check Valve Pipe Replacement .

Is the action complete?

Go to Step 48

Replace the AIR Pump Relay.

Is the action complete?

Go to Step 48

Replace the AIR Shut Off Valve. Refer to Secondary Air Injection Check Valve and Check Valve Pipe Replacement .

Is the action complete?

Go to Step 48

Replace the AIR Solenoid. Refer to Secondary Air Injection Check Valve and Check Valve Pipe Replacement .

Is the action complete?

Go to Step 48

Replace the AIR Pump. Refer to Secondary Air Injection Pump Replacement .

Is the action complete?

Go to Step 48

Replace the VCM.
Program the new VCM. Refer to VCM Replacement/Programming .
Perform the Passlock Reprogramming Procedure.
Perform the CKP System Variation Learn Procedure. Refer to Crankshaft Position System Variation Learn .

Is the action complete?

Go to Step 48

Install the scan tool.
Start the engine and allow it to run for 2 minutes.
Verify the engine is running at normal operating temperature and is in Closed Loop.
Command ON the AIR Pump with the scan tool.

Does the Short Term Fuel Trim indicate a change of more than the specified value within 30 seconds?

16%

System OK

Go to Step 4