Secondary air injection system

99-01 Blazers with the 4.3L motor and 00-03 2.2L
motors have the Secondary Air Injection system and I've listed the
codes, part #s, circuit description, and have to fix below.

DTC P0410 (SES Light On) - Secondary Air Injection
P1415 and/or P1416 for secondary air injection
Bank A and B can also be set if the powertrain control module (PCM)
detects a heated oxygen sensor voltage mismatch and activates an
internal test to confirm.

Circuit Description:
This is located under the radiator (pump,
electric solenoid, and vacuum shutoff valve) and tees off up to the
exhaust manifolds thru 2 check valves on 4.3L. For 4wd remove the front
skid plate to access. The secondary air injection pump is used to lower
tail pipe emissions on start-up. The PCM supplies a ground to the pump
relay, which energizes the pump and the electric solenoid valve. Engine
vacuum is applied to the shut-off valve when the solenoid is energized.
The engine vacuum opens the shut-off valve that allows air to flow to
the exhaust manifolds. Often the pump gets water/moisture in it and
freezes up blowing the fuse and the check valves rust or freeze open
internally and then burn threw the rubber hose, and even melt the lower
“T”, shutoff, and even pump impeller.

Check/Replace as required:
1. You should hear the pump on starting the
Blazer and if you put your hand on it you will feel it running for
about 1 minute. Part #12560095 (AC Delco 215-364) Pump, Sec Air Inj for
1999-2000 L35 (4.3L) or #12568324 (AC Delco 215-425) Pump, Sec Air Inj
for 2001 L35 (4.3L) + 2000-2003 L43/LN2 (2.2L).

The GM # is on your current pump so check it because the Dealer is very
confused and/or out of these and will sub other pumps. You can remove
the pump and take the #25 torx screws out and see if the impeller is
clogged, rusted, melted, etc before spending $100-200 for it. Impeller
should spin freely.

2. Extend the air intake hose that ends halfway
up the passenger side of the radiator about 2 more feet so it can run
between the battery and coolant reservoir and push into the fender hole to keep dry. 99-00 is 5/8 heater hose and inline connector and 01-03 is 3/4 heater hose and inline connector –check size.

3. #12558992 (AC Delco 215-638) air injection
check valves 2 required – most stores sell these for $12-20 each or
Dealer $33 each. If they rattle or the hoses are burned threw replace –
should only flow air into the exhaust. The easiest way is to remove the
two 13mm nuts that mount the check valve pipe to the exhaust manifold
and use a vise to hold them – trust me here. The little exhaust gaskets
should be reusable.

4. #10217106 connect (hoses) 2 required check
valves to pipes (Dealer Only $7 each). If burned threw or hard/brittle
replace. Usually a good thing to plan on buying!

5. #12555165 secondary injection shutoff valve
(vacuum operated in the ¾” hose in the pump outlet to the “T” pipe
under the Blazer (Dealer Only $27). Only open when the pump is on and
vac applied. Also replace the 5/32” vac hose from the solenoid to valve
and solenoid to intake (about 4 ft of it). Once you extend the air
intake listen to the hose end and you should not hear any exhaust noise
after the short initial one minute pump run – if you still do the vac
diaphragm is stuck open/clogged/burned so replace. Vac is applied by an
electric solenoid mounted by the pump #01997264. The center vac port
goes to the intake Manifold vac and the off center vac goes to the shutoff valve above. The vac
should only be applied to the shutoff valve for that 1 minute as the
Blazer starts then is switched off. Hose clamps will be needed here.

6. #10105352 “T” for under Blazer where pump
outlet to both pipes connect – if yours melted! One end is ¾” and two
are 5/8”ends - but you can use a ¾” on all ends with a little lube.
Hose clamps here too.

7. The pumps 30 amps Maxi-fuse (large size) is
under a little black cover between your battery tray and inside the
passenger side fender. You may have to remove your battery to get to
it. Depress the little cover retainer and remove, then pull the large
fuse out to check/replace. There’s also a 10 amp small fuse to check
for the electric solenoid that controls the secondary injection shutoff
valve mounted by the air pump.

8. If you need the 2 lower hoses that connect the
metal pipes to the “T” going to the pump here’s the bad news – Dealer
Only and includes the pipes so over $100.

Good luck and thank you for using Fixya.


99-01 Blazers with the 4.3L motor and 00-03 2.2L motors have the Secondary Air Injection system and I've listed the codes, part #s, circuit description, and have to fix below.

DTC P0410 (SES Light On) - Secondary Air Injection
P1415 and/or P1416 for secondary air injection Bank A and B can also be set if the powertrain control module (PCM) detects a heated oxygen sensor voltage mismatch and activates an internal test to confirm.

Circuit Description:
This is located under the radiator (pump, electric solenoid, and vacuum shutoff valve) and tees off up to the exhaust manifolds thru 2 check valves on 4.3L. For 4wd remove the front skid plate to access. The secondary air injection pump is used to lower tail pipe emissions on start-up. The PCM supplies a ground to the pump relay, which energizes the pump and the electric solenoid valve. Engine vacuum is applied to the shut-off valve when the solenoid is energized. The engine vacuum opens the shut-off valve that allows air to flow to the exhaust manifolds. Often the pump gets water/moisture in it and freezes up blowing the fuse and the check valves rust or freeze open internally and then burn threw the rubber hose, and even melt the lower “T”, shutoff, and even pump impeller.

Check/Replace as required:
1. You should hear the pump on starting the Blazer and if you put your hand on it you will feel it running for about 1 minute. Part #12560095 (AC Delco 215-364) Pump, Sec Air Inj for 1999-2000 L35 (4.3L) or #12568324 (AC Delco 215-425) Pump, Sec Air Inj for 2001 L35 (4.3L) + 2000-2003 L43/LN2 (2.2L).
The GM # is on your current pump so check it because the Dealer is very confused and/or out of these and will sub other pumps. You can remove the pump and take the #25 torx screws out and see if the impeller is clogged, rusted, melted, etc before spending $100-200 for it. Impeller should spin freely.

2. Extend the air intake hose that ends halfway up the passenger side of the radiator about 2 more feet so it can run between the battery and coolant reservoir and push into the fender hole to keep dry. 99-00 is 5/8 heater hose and inline connector and 01-03 is 3/4 heater hose and inline connector –check size.

3. #12558992 (AC Delco 215-638) air injection check valves 2 required – most stores sell these for $12-20 each or Dealer $33 each. If they rattle or the hoses are burned threw replace – should only flow air into the exhaust. The easiest way is to remove the two 13mm nuts that mount the check valve pipe to the exhaust manifold and use a vise to hold them – trust me here. The little exhaust gaskets should be reusable.

4. #10217106 connect (hoses) 2 required check valves to pipes (Dealer Only $7 each). If burned threw or hard/brittle replace. Usually a good thing to plan on buying!

5. #12555165 secondary injection shutoff valve (vacuum operated in the ¾” hose in the pump outlet to the “T” pipe under the Blazer (Dealer Only $27). Only open when the pump is on and vac applied. Also replace the 5/32” vac hose from the solenoid to valve and solenoid to intake (about 4 ft of it). Once you extend the air intake listen to the hose end and you should not hear any exhaust noise after the short initial one minute pump run – if you still do the vac diaphragm is stuck open/clogged/burned so replace. Vac is applied by an electric solenoid mounted by the pump #01997264. The center vac port goes to the intake Manifold vac and the off center vac goes to the shutoff valve above. The vac should only be applied to the shutoff valve for that 1 minute as the Blazer starts then is switched off. Hose clamps will be needed here.

6. #10105352 “T” for under Blazer where pump outlet to both pipes connect – if yours melted! One end is ¾” and two are 5/8”ends - but you can use a ¾” on all ends with a little lube. Hose clamps here too.

7. The pumps 30 amps Maxi-fuse (large size) is under a little black cover between your battery tray and inside the passenger side fender. You may have to remove your battery to get to it. Depress the little cover retainer and remove, then pull the large fuse out to check/replace. There’s also a 10 amp small fuse to check for the electric solenoid that controls the secondary injection shutoff valve mounted by the air pump.

8. If you need the 2 lower hoses that connect the metal pipes to the “T” going to the pump here’s the bad news – Dealer Only and includes the pipes so over $100.

Good luck and thank you for using Fixya.