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Secondary Air System Testing
 
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Pelican Technical Article:

Secondary Air System Testing

Nick Czerula

Time:

2 hours2 hrs

Tab:

$0

Talent:

*****

Tools:

Set of sockets 10mm, flathead screwdriver, plastic gasket scraper, hose clamp pliers, DVOM, test light, fused jumper wires.

Applicable Models:

BMW Z3 (1996-02)

Parts Required:

Secondary air pump, air valve and gasket, hose clamps; if needed

Hot Tip:

Replace any cracked or dry rotted hoses

Performance Gain:

Cleaner running engine

Complementary Modification:

Replace companion component

The secondary air system is used to improve catalytic converter efficiency and reduce the emission of harmful combustion byproducts in automotive exhaust. For a short period after a cold start, the catalytic converter is not hot enough to efficiently combine unburned fuel with available oxygen. An electric air pump forces fresh air into the exhaust stream just before the exhaust enters the catalyst. This extra air supplies the catalyst with additional oxygen, thus speeding up the combustion of unburned pollutants and raising catalyst temperature rapidly. When the catalyst reaches what is called "light-off temperature" (approximately 400-600 degrees F or 215-315 degrees C) it is capable of self-maintaining a high temperature and the high efficiency of combustion. At that point the secondary air system may be shut off.

A check valve is usually installed in the secondary air pump duct in order to prevent back flow of hot exhaust gases into the air pump.

The secondary air system is prone to faults that illuminate the check engine light. If you have fault codes for your secondary air, check the operation of the pump. You can test the function of the secondary air components using a BMW scan tool. If you do not have access to one, you can check secondary air pump function when starting the engine. When a cold engine is started, the secondary air pump will run for a calculated amount of time.  You can also manually test each item. In this tech article I will go over how to test each secondary air system component. The tests are going to be performed on a 1998 Z3 with a 4-cylinder engine. Relay, fuse and component locations may vary. The tests will however be similar. See our tech article on secondary air components replacing for location help. During these tests I will keep it simple and help you identify if the system needs to be tested further using a BMW scan tool.

To avoid marring the paint and trim, work with a plastic prying tool or wrap a screwdriver tip with masking tape before prying out body or interior items.

Keep in mind that when your car was serviced before, parts may have been replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have, so be prepared with different size sockets and wrenches. 

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If you're working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Do not work on your vehicle if you feel the task is beyond your ability. 

Vehicle models change and evolve, as they grow older, so the vehicle shown in our illustrations may vary slightly from yours. If something seems different, let us know and share your info to help other users. Do you have questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

The first thing to test is if the pump can turn on.
Figure 1

Secondary air pump: The first thing to test is if the pump can turn on. Locate the secondary air pump relay. It was located in the under hood fuse panel in my vehicle.

Remove the relay.
Figure 2

Secondary air pump: Remove the relay. On my vehicle the relay had a rubber cover. I had to unclip the relay from the panel using a small flathead screwdriver, then lever the rubber cover off the relay. Be careful not to tear the cover if you have this style. The green arrow points to the clip I had to release to remove the relay from the fuse panel.

Then using a fused jumper wire, jump terminals 30 and 87.
Figure 3

Secondary air pump: Then using a fused jumper wire, jump terminals 30 and 87. Use the bottom of the relay to identify the relay terminals. If the pump can be heard running move onto the next step. If it does not run, use the remaining steps under this heading for removing and bench testing the pump.

Using a flathead screwdriver, loosen the secondary air pump inlet hose clamp (green arrow).
Figure 4

Secondary air pump: Using a flathead screwdriver, loosen the secondary air pump inlet hose clamp (green arrow).

Then remove the secondary air inlet hose from the air filter housing by pulling it straight off (green arrow) then pull it off the air pump and store in a safe place.
Figure 5

Secondary air pump: Then remove the secondary air inlet hose from the air filter housing by pulling it straight off (green arrow) then pull it off the air pump and store in a safe place.

Next, you will unclip the three air filter housing retaining clips (green arrows).
Figure 6

Secondary air pump: Next, you will unclip the three air filter housing retaining clips (green arrows). One of the clips was hidden beneath the secondary air inlet hose. You will have to reach in behind air filter housing to access it.

Disconnect the intake air sensor electrical connector by pressing the wire release tab and pulling the connector straight off.
Figure 7

Secondary air pump: Disconnect the intake air sensor electrical connector by pressing the wire release tab and pulling the connector straight off.

Working at the air flow meter, twist electrical connector counterclockwise to disconnect (green arrow).
Figure 8

Secondary air pump: Working at the air flow meter, twist electrical connector counterclockwise to disconnect (green arrow). Then loosen the air flow meter hose clamp (yellow arrow). Once loose, remove the air filter housing from the engine compartment.

Then, loosen the secondary throttle body hose clamp at the rear air boot (green arrow).
Figure 9

Secondary air pump: Then, loosen the secondary throttle body hose clamp at the rear air boot (green arrow).

Once loose, pull the intermediate throttle out of the boot.
Figure 10

Secondary air pump: Once loose, pull the intermediate throttle out of the boot. You can leave the cables connected, just lay it aside.

Next you have to disconnect the secondary air pipe from the pump.
Figure 11

Secondary air pump: Next you have to disconnect the secondary air pipe from the pump. Squeeze the release tabs, then pull the pipe straight off the secondary air valve to remove.

Now it is time to unbolt the secondary air pump.
Figure 12

Secondary air pump: Now it is time to unbolt the secondary air pump. You will have to lift it up to disconnect the electrical at the bottom. Start by removing the two 13mm nuts (green arrows) that secure the pump to the support bracket.

Then working at the back side of the pump bracket, remove the wiring harness from the mounting clip (green arrow).
Figure 13

Secondary air pump: Then working at the back side of the pump bracket, remove the wiring harness from the mounting clip (green arrow).

Lift the pump up and off the bracket.
Figure 14

Secondary air pump: Lift the pump up and off the bracket. You will have to push the pump toward the firewall to clear the plastic clip on the rear of the bracket. Then, remove the purge valve from the pump by pulling it straight up and off the mounting bracket (green arrow). The purge valve is housed in a rubber mount, if it is stuck; lubricate it with dish soap to help get it off.

Lift the secondary air pump off the mounting bracket and disconnect electrical connector by squeezing tabs and pulling is straight off.
Figure 15

Secondary air pump: Lift the secondary air pump off the mounting bracket and disconnect electrical connector by squeezing tabs and pulling is straight off.

With the air pump remove, use a jumper wire from battery ground to terminal 1 (green arrow).
Figure 16

Secondary air pump: With the air pump remove, use a jumper wire from battery ground to terminal 1 (green arrow). Then use a fused jumper to battery positive and terminal 2 (red arrow). The pump should turn on. If it does not, replace the pump. Use the electrical connector to determine pin locations. A quick rule of thumb; BMW makes ground wires brown. This may help identify the circuit easier. If there is any doubt, consult a wiring diagram. To install the pump, reverse the steps. Be sure to clip the wiring harness to the bracket and double check the hose routing.

Secondary air pump solenoid - This secondary air pump solenoid is located near the oil filter on the intake manifold (green arrow).
Figure 17

Secondary air pump solenoid: - This secondary air pump solenoid is located near the oil filter on the intake manifold (green arrow).

The test it, start by pressing the wire release tab and pulling the electrical connector straight off.
Figure 18

Secondary air pump solenoid: The test it, start by pressing the wire release tab and pulling the electrical connector straight off.

Next you have to slide the solenoid off the mounting bracket.
Figure 19

Secondary air pump solenoid: Next you have to slide the solenoid off the mounting bracket. To do this, I use a small flathead screwdriver to press the release tab, then slide it off toward the left side of the vehicle. See next photo and step for what the tab you have to disconnect looks like.

The green arrow points to the plastic tab you unclipped in the previous step.
Figure 20

Secondary air pump solenoid: The green arrow points to the plastic tab you unclipped in the previous step. The yellow arrows point to the vacuum hoses. The hose with the blue tracer is feeds the check valve. The hose with the white tracer is the manifold vacuum source. With the engine running, there should be constant engine vacuum at the white hose. If there isnÂ't, the hose may be broken or restricted. Once you have confirmed there is sufficient vacuum to the solenoid, activate the solenoid to see if the vacuum gets to the check valve.

To test it, start by removing the vacuum hose from the secondary air check valve.
Figure 21

Secondary air pump solenoid: To test it, start by removing the vacuum hose from the secondary air check valve.

Make sure both vacuum hoses are connected to the solenoid.
Figure 22

Secondary air pump solenoid:Make sure both vacuum hoses are connected to the solenoid. Then unplug electrical connector. Then, install a vacuum gauge into the vacuum hose at the secondary air check valve. Use a jumper wire from battery ground to terminal 1 (green arrow). Then use a fused jumper to battery positive and terminal 2 (red arrow). The solenoid should turn activate. The vacuum gauge you installed should read manifold vacuum. If it does not, the solenoid is faulty. If it does, move onto the next step.

Secondary air pump check valve - The secondary air pump check valve is located at the right front of the cylinder head.
Figure 23

Secondary air pump check valve: - The secondary air pump check valve is located at the right front of the cylinder head. Start by removing the vacuum hose from the secondary air check valve.

Next you will have to remove the secondary air valve is to disconnect the air pipe.
Figure 24

Secondary air pump check valve:  Next you will have to remove the secondary air valve is to disconnect the air pipe. Squeeze the release tabs, then pull the pipe straight off the secondary air valve to remove. Start the engine. The valve should not leak exhaust out the hose fitting toward the air pump. There may be a slight exhaust pulse noise, if should not be loud.

Then connect a hand vacuum pump to the secondary air check valve vacuum fitting.
Figure 25

Secondary air pump check valve: Then connect a hand vacuum pump to the secondary air check valve vacuum fitting. Apply vacuum to the valve, the valve should open as you apply vacuum and close as you bleed the vacuum off. If all tests are complete and a fault code is still present and there is no sign of a faulty component, you will have to use a BMW scan too run the system test. When the air pump is commanded on, the DME looks at the oxygen sensor signal. The DME expects the signal to read lean, if it does not a fault code is set. You may have a low flow issue, this could be due to a possible restriction. However this is unlikely. Most failures I see are vacuum hoses, solenoids and check valves.

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Comments and Suggestions:
anton Comments: Hi. my z3 is 1996 1.9lts said second air scanner error. I'm seeing this article and my car does not have the pump below the airbox .. where is it? Nor has the valve to the right of the engine head. It will be different than mine?
Thank you
July 8, 2016
  Followup from the Pelican Staff: Is your a US model? I am not aware of a different location.- Nick at Pelican Parts  
Bman Comments: I am replacing the air pump check valve on my bmw 318ti. Does it require some kind of gasket sealer before putting it back together?
July 8, 2016
  Followup from the Pelican Staff: Yes, there is a valve gasket. Give The Pelican Parts parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 
Mike Comments: Air pump on a2.8 z3 is making noise when first starting car,does that mean I'll need to replace it.?
March 29, 2015
  Followup from the Pelican Staff: It should make some noise, like a loud hair dryer. Is is worse than that? It may be faulty. - Nick at Pelican Parts  

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Page last updated: Sat 12/3/2016 02:07:50 AM