Smog Trouble. Help!

MORDANTCHRIS

MEMBER
CHEVROLET

This question is regarding a 1999 Chevrolet s10 Blazer, 4.3L V6.
My trouble started a few months ago with a check engine light. I scanned the computer and found a P0410 code (Secondary Air Intake Failure). I researched and found that the smog pump was probably bad. I replaced the smog pump, cleared the code. The code came back, same thing.
I checked an inline fuse that comes from the smog pump, it is supposed to blow when the smog pump fails. It was intact.
I researched again and found that there are one way vavles after the smog pump that are there so the air only flows one way into the exhaust. I replaced those, the code stayed away a little longer but still came back.
I don't know what else to do. The O2 sensors appear to be ok. Maybe they aren't. Has anyone ever seen this? Does anyone have a solution or an idea?
Please help. I am way over my smog date right now.

1 Reply

MIKEYBDMAN

MECHANIC
623 POSTS

Here is what I found. Hope it helps.
Circuit Description
An AIR Pump is used on this vehicle to lower tail pipe emissions at start-up. The VCM supplies a ground to the AIR Pump Relay, which energizes the AIR Pump and the AIR Solenoid.

When the AIR Pump is enabled, the VCM monitors the HO2S voltage. If the HO2S voltages go below a calibrated threshold value, the VCM interprets this as an indication that the AIR System is operational. When the AIR Pump is disabled, the VCM monitors the HO2S voltages. The HO2S voltages should increase above a calibrated threshold value and switch normally.
If the VCM did not sense more than a predetermined amount of HO2S rich switches, a malfunction will be reported.

The VCM will activate the AIR Pump during closed loop operation. When the AIR System is activated, the VCM will monitor the HO2S voltages and short term fuel trim values for both banks of the engine. If the AIR System is operating properly, the HO2S voltages should go low and the short term fuel trim should go high.

The VCM checks that the HO2S voltages return to above a rich threshold when the AIR Pump is disabled.

If the VCM determines that the HO2S voltages for both banks did not respond as expected during the tests, DTC P0410 will set. If only one sensor responded, the VCM will set either a DTC P1415 or P1416 to indicate on which bank the AIR System is inoperative.

Conditions for Running the DTC

No active ECT sensor DTCs
No active IAC sensor DTCs
No active HO2S DTCs
No active misfire DTCs
No active MAP DTCs.
No active Fuel Trim DTCs
No active EVAP DTCs
No active TP Sensor DTCs
No active IAT DTCs
No active MAF DTCs
The MAF is less than 25 g/s
The commanded air/fuel ratio is 14.7:1
The engine load is less than 34 percent
Power enrichment mode is not active
DFCO (Decel Fuel Cutoff Mode) is not active
Catalyst overtemp protection is not active
The system has been in closed loop mode for more than 20 seconds
The short term fuel trim is between 124-132 counts
The engine speed is more than 550 RPM
The ECT is between 80-110°C (176-230°F)
The system voltage is 11.7 volts or more
Conditions for Setting the DTC

The O2 sensor voltage is less than 222 mv for more than 1.3 seconds, or
The short term fuel trim value changes more than 20 percent when the secondary air injection pump is turned on and the system is in closed loop operation.
Action Taken When the DTC Sets

The VCM illuminates the MIL during the second consecutive drive cycle in which the diagnostic reports a fail.
The VCM will set the DTC and records the operating conditions at the time the diagnostic fails. The VCM stores the failure information in the scan tools Freeze Frame and/or the Failure Records.
Conditions for Clearing the MIL/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 (coolant temperature has risen 22°C (40°F) from the start-up coolant temperature and the engine coolant temperature is more than 70°C (158°F) during the same ignition cycle).
Use the scan tool Clear Information function.
Diagnostic Aids
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
Leaks or restrictions in the vacuum hoses for the AIR Shut Off Valve.
An AIR supply hose that is melted before the check valve could indicate exhaust gas back-flow past the check valve.

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. See: Diagnosis By Symptom (Computers and Control Systems)

Test Description
Numbers below refer to the step numbers on the Diagnostic Table.

This step will determine if the AIR System is functioning correctly.
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 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.