ENGINE LIGHT COMES ON
Step 1:
What does tP0411 Secondary Air Injection System Incorrect Flow DetectedWhat does that mean?
Secondary Air Injection is an emission control that uses an air pump
(either electric or turned by the drive belt) to move fresh air into the
exhaust
manifold(s) or exhaust ports when the engine is in open loop and
pre-catalytic converter when in closed loop. This reduces hydrocarbon
emissions (HC), Carbon Monoxide (CO), and oxides of Nitrogen (NOx). This
fresh air helps convert Carbon Monoxide (CO) into Carbon Dioxide (CO2)
and Hydrocarbons (HC) into water vapor (H20).
A check valve is located in the air supply line to keep exhaust
gasses from flowing into the pump. A cutoff valve that controls the
airflow may be vacuum controlled or electrically controlled. When the
powertrain control module (PCM) activates the valve, vacuum travels to
the cutoff valve to open it and allow fresh air to flow. Some systems
may have only a check valve and the flow may be regulated by a
electromagnetic clutch on the air pump (similar to an A/C clutch).
Under hard acceleration, the air pump will be deactivated to prevent
backfiring in the exhaust. To self-check, the AIR system will be
activated by the PCM and fresh air would be routed into the exhaust
system. The oxygen sensors would sense this fresh air as a lean
condition and the short term fuel
trims would begin to move in the positive direction to compensate. The
PCM expects to see this happen within just a few seconds during the self
test. If it does not see the short term fuel trims rise, then the PCM interprets this as a malfunction in the AIR system and a code will be recorded.Step 2:
Symptoms
Symptoms of a P0411 DTC may include:
Causes
Potential causes of a P0411 code include:
Step 3:
Possible Solutions
If you have access to a scan tool, with KOEO (Key on engine off)
command the AIR pump on. It should activate. If it doesn't, remove and
inspect the AIR pump relay for discoloration/melting due to heat. Repair
as necessary.
With the ignition on (engine off) check for battery voltage at the
switched battery feed to the relay and the relay control circuit. If
either of these isn't present, inspect circuit for blown fuse or
open/short in the wiring. Repair cause of short and retest. If they are
both present, jumper the battery feed to AIR pump feed circuit using a
fused jumper. The pump should activate. If not, check for power
and ground present at the AIR pump when jumpered. If there is no
voltage/ground present at pump repair open in wiring harness. If voltage
and ground is present, but pump still does not run, suspect a bad AIR
pump. If after jumpering the AIR pump feed circuit the pump activates
then the problem is likely the AIR pump relay. Replace and retest.
If the scan tool activates the AIR pump, with KOER (Key on engine
running) activate the AIR pump solenoid valve on and see if there is
vacuum to the cutoff valve. It should have vacuum present to open the
valve. If there is no vacuum present, check the AIR pump's vacuum
solenoid valve for vacuum supply from the manifold. If there is vacuum
present then the vacuum solenoid is likely bad. Replace it. If there is
no vacuum present at the supply to the vacuum solenoid, check for a
plugged or damaged vacuum line or plugged vacuum port. But if there is
vacuum present at the cut-off valve, shut the engine off and using a
vacuum pump, apply vacuum to the cut-off valve and see if it holds a
vacuum and that air flows through it when vacuum is applied. If it
doesn't hold vacuum or the valve doesn't flow when vacuum is applied,
replace the cut-off valve. If the cut-off valve works properly, inspect
the check valve for obstruction or to see if it's missing. Replace as
necessary.
Check the steel line to the exhaust catalyst as well as the exhaust ports for damage or holes that could give a false reading.
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