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Pelican Technical Article:

M54 Engine Secondary Air System Testing

Nick Czerula

Time:

2 hours2 hrs

Tab:

$250

Talent:

***

Tools:

Sockets 13 10 mm, flathead screwdriver, plastic gasket scraper

Applicable Models:

X3 E83 (2004-06)
X3 E83 facelift (N/A-A)

Parts Required:

Secondary air pump, air valve and gasket, air hose

Hot Tip:

Replace any cracked or dry rotted hoses

Performance Gain:

Working secondary air

Complementary Modification:

Replace engine air filter

An electric air pump (red arrow) forces fresh air into the exhaust stream just before the exhaust enters the exhaust manifold (blue arrow).
Figure 1

An electric air pump (red arrow) forces fresh air into the exhaust stream just before the exhaust enters the exhaust manifold (blue arrow).

To test the pump, I suggest removing the outlet hose and gaining access to the electrical connector.
Figure 2

To test the pump, I suggest removing the outlet hose and gaining access to the electrical connector. First you have to disconnect the secondary air pipe from the pump to valve connection (yellow arrow). Once the hose is removed, disconnect the electrical connector (red arrow) See following steps.

Squeeze the collar (red arrows), and then pull the pipe straight off the secondary air pump and air pump check valve to remove.
Figure 3

Squeeze the collar (red arrows), and then pull the pipe straight off the secondary air pump and air pump check valve to remove. The valve connection (blue arrow) may be corroded. If so, wiggle the hose back and forth as you pull it off. A small amount of penetrating oil may also help free it up.

Working at the bottom of the pump, disconnect electrical connector (inset) by squeezing tabs and pulling is straight off.
Figure 4

Working at the bottom of the pump, disconnect electrical connector (inset) by squeezing tabs and pulling is straight off. Once off, you can test for voltage at the wires. The pump is supplied constant ground to terminal 1 (blue arrows) and switched power to terminal 2 (red arrows).

The easy way to test the entire system is by using the built in system test found in most advanced BMW scan tools.
Figure 5

The easy way to test the entire system is by using the built in system test found in most advanced BMW scan tools. However, this isn't an option for most of us.

With an advanced scan tool, you can also activate individual components like the pump or relay (red arrow).
Figure 6

With an advanced scan tool, you can also activate individual components like the pump or relay (red arrow). Very helpful, but once again not always available to most of us. I will show you how to activate the pump manually for testing, in the case you aren't one of the lucky ones.

Remove the glove box.
Figure 7

Remove the glove box. See our tech article on glove box replacing. Then, locate the secondary air relay (red arrow), otherwise known as K6304a.

Remove the relay from the electrical box by squeezing the release tab (red arrow) and sliding the relay toward the firewall (blue arrow).
Figure 8

Remove the relay from the electrical box by squeezing the release tab (red arrow) and sliding the relay toward the firewall (blue arrow). Release tab shown with relay already removed for clarity.

With the relay removed, you can identify the terminals and functions.
Figure 9

With the relay removed, you can identify the terminals and functions. Terminal 30 (red arrow) is constant power to the relay from F36. This should have battery positive volts all the time. Terminal 85 (yellow arrow) is the battery negative side of the low current switch. This should be close to zero volts with the key ON. Terminal 86 (purple arrow) is the battery positive to the relay from Fuse F03. Terminal 87 (blue arrow) is the battery positive output to the secondary air pump. Terminal 87a (white arrow) is not used on my model. To activate the pump manually, used a fused jumper wire and jump terminals 30 and 87. The pump should run when this is jumped.

Connect a test light or DVOM (red arrow) across the air pump electrical connector terminals.
Figure 10

Connect a test light or DVOM (red arrow) across the air pump electrical connector terminals. Jump the relay or activate the pump test. The test light will light. The DVOM will read Battery volts (voltage the battery is at, 12 volts for example). Keep in mind, a test light may light with a low supply voltage. I suggest load testing using a test light (blue arrow) and a DVOM. Connect the DVOM across the secondary air pump electrical connector terminals and take a reading. It should read battery volts when the engine is started or the pump is commanded on. Then connect an incandescent bulb style test light to the battery ground and touch the test light probe tip to the positive wire you are backprobing with the DVOM. Your reading should hold steady. A maximum drop in voltage of 0.5 volts is OK. Anything more is a problem. If you find a problem with the connector, replace the pigtail with a new one. Cut the harness back enough to find good, clean wire, then butt connect and seal the harness.

To test the check valve, remove the hose.
Figure 11

To test the check valve, remove the hose. With the fitting open (red arrow) start the engine. Little to no exhaust should be heard escaping. If you have exhaust pulsing out of the valve, replace it.

Next you can test the flow meter for the pump (white arrow).
Figure 12

Next you can test the flow meter for the pump (white arrow). If you have a fault code for pump flow or low flow, this might be the part you have to replace. First confirm the pump runs. Then with the key on you can test voltage at the connector. Terminal 1 is ground (blue arrow), terminal 2 is battery positive (red arrow) and terminal 3 is the signal (yellow arrow).

Plug in the sensor connector, backprobe terminal 3 (red arrow).
Figure 13

Plug in the sensor connector, backprobe terminal 3 (red arrow). Activate the pump using a scan tool or by jumping the relay. Your DVOM should display about 3.5: 4.0 volts when air is flowing. When air is not flowing, it will be close to zero volts. If flow is low but the pump is running, check that the filter is not plugged.

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Page last updated: Wed 12/7/2016 03:08:53 AM