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E46 Xi Forum
The E46 XI was produced from 01-05 in sedan and touring body styles. Powered by either a 2.5L inline 6 in the 325xi or a 3.0L inline 6 330xi. Discuss all thing about BMW AWD E46 'Xi' here.

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Old 09-21-2014, 01:57 PM   #1
psuryava81
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My Ride: 2005 325xi
Secondary air pump system P0491 and P0492

Hi All,
I am a first time owner of 2005 BMW 235xi. My inspection failed for emissions. It turns out the OBD was not ready. I drove 100 miles and there was a "Service Engine Soon" light. I knew it was not going to be good. The dealer had duped me into believing there was no issues. The codes were the common P0491 and P0492. I have checked the following things.

1. Pump wont start at cold-start
2. The pump wont run on a 12V battery
3. I checked the power connecter with Digital Multimeter at cold-start and there is no power.
4. I checked the fuses in the fuse box under-hood (30A and 20A) and the Glove-Box(50A). All are fine.
5. Next I verified the relay is also good. I connected 12V battery to the relay and it clicked. Then I verified continuity on the other leads with and without battery. All is fine as it should.

The rest is out off my depth. I am assuming the valve is toast too. But I dont understand why there is no power at the Air Pump connector. Any help will be appreciated.

Thank You
Prashant
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Old 09-21-2014, 03:36 PM   #2
jfoj
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Is your car really a 2005? If so, it should have a SAP system like the on pictured in this thread - http://forum.e46fanatics.com/showthread.php?t=965526

With the codes you are stating, it appears that you may have the older vacuum controlled Kombi valve system without the SAP that has the input MAF of the pump is running or the O2 sensors are probably lazy?? If the pump is not running and it is the style with the input MAF you should have a P0411 code.

Post Freeze Frame data. Do you have an OBDII scan tool? If not buy an OBDII App for a smart phone and interface for under $35, you WILL need it to get through this mess!

Please verify if you have the newer style SAP system with the MAF.

Here are a few things to understand.

1. The SAP will not run once the engine coolant temp is 100F or higher. It will also turn off at 100F.

2. Make sure the SAP is able to turn freely.

3. You may have O2 sensor issues, read this thread - http://forum.e46fanatics.com/showthread.php?p=16203126

Not O2 sensors do not have anything to do with triggering the pump to run.

Keep in mind, you stated the pump would not run with 12 Volts directly connected to the pump?? so this means the pump may be bad, but you also say there is not 12 Volts to the pump on cold start??

There seems to be a LOT of questions as to what is going on here.

SAP should be the easiest and first Readiness Monitor to clear.
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Hidden OBC Menu - Check Voltage, Temps, Fuel Level - http://forum.e46fanatics.com/showthread.php?t=239619

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Last edited by jfoj; 09-21-2014 at 03:42 PM.
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Old 09-21-2014, 04:00 PM   #3
psuryava81
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I am very sure my car does not have SAP system. In the pic you mentioned there are two hoses on the Air Pump. One on the side is going to the Check Valve and the other one on the top is going to the Black thing. The Air Pump on my car has only one hose on the side, which is going to the check valve.

Does COLD Start mean the outside temperature also has to be below certain value? Or is it just the engine and the CAT temperature?
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Old 09-21-2014, 04:10 PM   #4
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Quote:
Originally Posted by psuryava81 View Post
I am very sure my car does not have SAP system. In the pic you mentioned there are two hoses on the Air Pump. One on the side is going to the Check Valve and the other one on the top is going to the Black thing. The Air Pump on my car has only one hose on the side, which is going to the check valve.

Does COLD Start mean the outside temperature also has to be below certain value? Or is it just the engine and the CAT temperature?
You need to take a picture of your SAP system. All of these cars have a SAP system.

You may have a cobbled up car where someone put the wrong pump on your car IF it is really a 2005 model.

Look the VIN sticker in the door and tell me what the build month/year is on the door jam sticker.

The engine coolant temperature has to be below 100F, so it is best to check things when the car has sat overnight if you do not have an OBDII tool that reads real time data or you can see the 4th link below in my signature to pull up the Hidden OBC Menu and you can monitor the engine coolant temperature directly on the dashboard.
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Fuel pump failures - http://forum.e46fanatics.com/showthread.php?t=929501

Temp Info - http://forum.e46fanatics.com/showthread.php?t=964491

Hidden OBC Menu - Check Voltage, Temps, Fuel Level - http://forum.e46fanatics.com/showthread.php?t=239619

E46/E39 GM5 Door Lock Info - www.bmwgm5.com

Lower hose fan switch O-ring - BMW #13621743299
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Old 09-21-2014, 04:26 PM   #5
psuryava81
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The sticker says 11/04. In that case 2005 makes sense.
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Old 09-21-2014, 05:10 PM   #6
jfoj
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Yes, 11/04 should be a 2005 model.

But what is strange RealOEM.com shows that the your car should have the SAP system like I posted in the thread on the P0411.

As I recall BMW swapped over to these MAF based SAP systems in late 2003, and to my knowledge all later cars had the MAF based SAP system.

So this is why I need to see pictures of your airpump and all the hoses as well as the Kombi valve so we can determine what is right and what is wrong with your installation.

I am confused why there is no P0411 unless for some reason if the P0491/P0492 somehow do over ride the P0411 popping up and/or the P0411 will not pop if the SAP MAF has been removed?

Hopefully the problem is as simple as the wrong SAP pump installed and the SAP MAF has been removed?

It is possible that if the SAP MAF was removed this may be inhibiting the SAP pump from running? As I recall on my car when the SAP MAF was bad, the pump ran for about 5 seconds, then shut down. I never unplugged the SAP MAF to see if the SAP did not run at all, but this is something I could try if needed.

Pictures will be the best way to move forward from here. Try to get pictures of any brackets and wiring behind the SAP pump back toward the firewall as well.
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Temp Info - http://forum.e46fanatics.com/showthread.php?t=964491

Hidden OBC Menu - Check Voltage, Temps, Fuel Level - http://forum.e46fanatics.com/showthread.php?t=239619

E46/E39 GM5 Door Lock Info - www.bmwgm5.com

Lower hose fan switch O-ring - BMW #13621743299
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Old 09-21-2014, 05:18 PM   #7
LD330XI
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FYI: the e46 xi models never received any updates for the ecu or wiring. Even my 05 xi has a ms43 ecu, and no maf on the sap.

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Last edited by LD330XI; 09-21-2014 at 05:25 PM.
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Old 09-21-2014, 05:36 PM   #8
jfoj
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Originally Posted by LD330XI View Post
FYI: the e46 xi models never received any updates for the ecu or wiring. Even my 05 xi has a ms43 ecu, and no maf on the sap.
That's interesting, not what RealOEM was showing for both the '04/'05 325xi and 330xi!

I have not seen any xi's later than 2003 as I recall.

This is why I want to see pictures of what the OP has, I have seen some situations where the wrong year SAP was cobbled onto cars causing all sorts of issues.

This is why I was confused with the P0491/P0492 as I do not recall these codes showing up on MAF based SAP systems.
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Temp Info - http://forum.e46fanatics.com/showthread.php?t=964491

Hidden OBC Menu - Check Voltage, Temps, Fuel Level - http://forum.e46fanatics.com/showthread.php?t=239619

E46/E39 GM5 Door Lock Info - www.bmwgm5.com

Lower hose fan switch O-ring - BMW #13621743299

Last edited by jfoj; 09-21-2014 at 05:37 PM.
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Old 09-21-2014, 07:42 PM   #9
psuryava81
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I have attached an image from the internet which is exactly what my car looks like. I will get pics tomorrow morning. I have also attached the image from realoem that matches my car.


http://www.realoem.com/bmw/showparts...88&hg=11&fg=50
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Old 09-21-2014, 08:56 PM   #10
jfoj
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OK, we will start over with the assumption that the xi cars never had the MAF based SAP systems.

So you should have a SAP pump with a single output hose, a vacuum controlled Kombi valve, a vacuum hose that runs along the valve cover to a vacuum solenoid that is mounted on the underside of the rear of the intake manifold..

First thing you need to make sure the SAP pump actually will run, the pump bearings get bad over the years and the pump can seize.

The things to check are the following.

1. Does the SAP pump run?
2. Is the SAP pump output hose not cracked or collapsed internally?
3. Does the vacuum controlled Kombi valve have good hose between the Kombi valve and the solenoid under the intake?
4. Can you verify if the SAP relay engages and has 12 Volts at the output of the relay?
5. Make sure Fuse 3/20 Amp fuse in the DME fuse carrier is good.
6. Make sure Fuse 36/50 Amp in the main fuse panel is good.

Once you get the SAP system working, then if the O2 sensors are lazy you still may have P0491/P0492 but this can be addressed once the pump runs.

Expect the pump to run for up to 90 seconds or until the engine coolant temperature reaches 100F.
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Fuel pump failures - http://forum.e46fanatics.com/showthread.php?t=929501

Temp Info - http://forum.e46fanatics.com/showthread.php?t=964491

Hidden OBC Menu - Check Voltage, Temps, Fuel Level - http://forum.e46fanatics.com/showthread.php?t=239619

E46/E39 GM5 Door Lock Info - www.bmwgm5.com

Lower hose fan switch O-ring - BMW #13621743299
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Old 09-21-2014, 09:22 PM   #11
psuryava81
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The things to check are the following.

1. Does the SAP pump run? -----No
2. Is the SAP pump output hose not cracked or collapsed internally?----- Looks good
3. Does the vacuum controlled Kombi valve have good hose between the Kombi valve and the solenoid under the intake?-----Have to check
4. Can you verify if the SAP relay engages and has 12 Volts at the output of the relay?-------Yes
5. Make sure Fuse 3/20 Amp fuse in the DME fuse carrier is good.------All good
6. Make sure Fuse 36/50 Amp in the main fuse panel is good.------All good
7. No power at Air Pump connector at cold start.

Can there be any other reason for no power at the Pump other than the Fuses and Relay???
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Old 09-21-2014, 09:56 PM   #12
jfoj
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Quote:
Originally Posted by psuryava81 View Post
The things to check are the following.

1. Does the SAP pump run? -----No
2. Is the SAP pump output hose not cracked or collapsed internally?----- Looks good
3. Does the vacuum controlled Kombi valve have good hose between the Kombi valve and the solenoid under the intake?-----Have to check
4. Can you verify if the SAP relay engages and has 12 Volts at the output of the relay?-------Yes
5. Make sure Fuse 3/20 Amp fuse in the DME fuse carrier is good.------All good
6. Make sure Fuse 36/50 Amp in the main fuse panel is good.------All good
7. No power at Air Pump connector at cold start.

Can there be any other reason for no power at the Pump other than the Fuses and Relay???
Bad/Melted connection or problem with the relay.

Suggest you use a test light to verify BOTH the postive/12 Volt feed and ground path.

If the pump will not run, it may have shorted and caused a problem.

If you are confident the pump does not run/work, suggest you source a replacement pump. Maybe even from a scrap yard, as long as you get a pre-3/2003 car, the pump should not have the intake hose in the center.

Then move on from there.

The relay needs to kick in on cold start regardless if power is present at the output of the relay.

Sounds like you have multiple issues and maybe someone made matters worse working on trying to solve the problem at one point?
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Fuel pump failures - http://forum.e46fanatics.com/showthread.php?t=929501

Temp Info - http://forum.e46fanatics.com/showthread.php?t=964491

Hidden OBC Menu - Check Voltage, Temps, Fuel Level - http://forum.e46fanatics.com/showthread.php?t=239619

E46/E39 GM5 Door Lock Info - www.bmwgm5.com

Lower hose fan switch O-ring - BMW #13621743299
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Old 09-21-2014, 10:59 PM   #13
psuryava81
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I tested the Relay with a 12V Battery. I heard it click and also the other leads had continuity. There must be something else which causes the Relay to engage and supply power to the SAP? I am guessing some Temperature sensor maybe.

Last edited by psuryava81; 09-21-2014 at 11:07 PM.
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Old 09-21-2014, 11:16 PM   #14
jfoj
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I tested the Relay with a 12V Battery. I heard it click and also the other leads had continuity. There must be something else which tells the Relay to engage and supply power to the SAP?
Testing the relay for continuity does not mean the relay is good. The SAP pulls a LOT of current and the contacts may be burnt.

This is why a test like is wise over a meter.

Then you can also see if the relay is triggered on cold start and if power is being passed by the relay.

All I really care about is the DME grounding pin 4 on the relay socket at cold start, it is does, then the problem should not DME related. Use a test light with the clip to a positive power point and the probe end to port 4 in the relay socket.
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Solve your misfires, lean codes, rough idle - http://forum.e46fanatics.com/showthread.php?t=897616

Fuel pump failures - http://forum.e46fanatics.com/showthread.php?t=929501

Temp Info - http://forum.e46fanatics.com/showthread.php?t=964491

Hidden OBC Menu - Check Voltage, Temps, Fuel Level - http://forum.e46fanatics.com/showthread.php?t=239619

E46/E39 GM5 Door Lock Info - www.bmwgm5.com

Lower hose fan switch O-ring - BMW #13621743299
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Old 09-22-2014, 07:54 AM   #15
psuryava81
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What positive point will be handy and safe to use in the glove box area. I want to be sure as I dont want to fry any electrical systems.
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Old 09-22-2014, 08:03 AM   #16
jfoj
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IF, the test light cable is long enough you can just pop the hood and connect to the positive jump start point under the hood.

If the test light cable is not long enough or big enough to the positive jump start post, use a jumper cable as an extension, however, BE CAREFUL to make sure the jumper cable does not touch any part of the car, you may want to wrap the connection is a plastic bag/towel for a safe measure until you are done testing.

Not sure there is a SIMPLE and EASY connection to be made under the dash?

One thing you could try is a wire or wire with a male spade connector on it plugged into position 8 in the relay socket, then the tip of the test light connected/touching position 4 in the relay socket when the car is first started.

If the light comes on in this configuration it confirms that the DME and the power to the coil relay is good with a single test. But if this does not work, you then need to narrow down if the problem is the DME control or the power to terminal 8 in the relay socket.

Terminal 2 in the relay socket should have 12 Volts all time, this is the 50 Amp feed for the pump.
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Solve your misfires, lean codes, rough idle - http://forum.e46fanatics.com/showthread.php?t=897616

Fuel pump failures - http://forum.e46fanatics.com/showthread.php?t=929501

Temp Info - http://forum.e46fanatics.com/showthread.php?t=964491

Hidden OBC Menu - Check Voltage, Temps, Fuel Level - http://forum.e46fanatics.com/showthread.php?t=239619

E46/E39 GM5 Door Lock Info - www.bmwgm5.com

Lower hose fan switch O-ring - BMW #13621743299
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Old 09-22-2014, 10:23 AM   #17
psuryava81
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Those are some awesome tips. I cant wait to get off work and try it. I was also thinking if the light works on terminal 4 then I can short terminal 2 and 6 with spade connectors. This should definitely send power to the SAP connector. Let me know if that is a safe thing to do. That would narrow down the issue.
I am ordering the SAP unit and the valve. I will the order the relay too.
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Old 09-22-2014, 10:32 AM   #18
jfoj
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Originally Posted by psuryava81 View Post
Those are some awesome tips. I cant wait to get off work and try it. I was also thinking if the light works on terminal 4 then I can short terminal 2 and 6 with spade connectors. This should definitely send power to the SAP connector. Let me know if that is a safe thing to do. That would narrow down the issue.
I am ordering the SAP unit and the valve. I will the order the relay too.
Not sure would jump on the Kombi valve, the do not fail often.

You should be able to jump 2 to 6 and send power to the pump connector.

To be safe, you can unplug the pump, use the test light as a jumper, it should not light up if the pump is disconnected and limit the current flow, you should then be able to measure Voltage with a meter at the connector.

Then if you decide to use a jumper, this will be fine, but do not jumper things if you think the motor is bad.
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Solve your misfires, lean codes, rough idle - http://forum.e46fanatics.com/showthread.php?t=897616

Fuel pump failures - http://forum.e46fanatics.com/showthread.php?t=929501

Temp Info - http://forum.e46fanatics.com/showthread.php?t=964491

Hidden OBC Menu - Check Voltage, Temps, Fuel Level - http://forum.e46fanatics.com/showthread.php?t=239619

E46/E39 GM5 Door Lock Info - www.bmwgm5.com

Lower hose fan switch O-ring - BMW #13621743299
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Old 09-22-2014, 02:29 PM   #19
psuryava81
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The DME also drives the vaccum valve circuit right ? I am unable to find any wiring diagram for that.
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Old 09-22-2014, 02:35 PM   #20
jfoj
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Rarely have I seen power problems with the SAP vacuum solenoid. More problems with the vacuum lines breaking/deteriorating.
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Solve your misfires, lean codes, rough idle - http://forum.e46fanatics.com/showthread.php?t=897616

Fuel pump failures - http://forum.e46fanatics.com/showthread.php?t=929501

Temp Info - http://forum.e46fanatics.com/showthread.php?t=964491

Hidden OBC Menu - Check Voltage, Temps, Fuel Level - http://forum.e46fanatics.com/showthread.php?t=239619

E46/E39 GM5 Door Lock Info - www.bmwgm5.com

Lower hose fan switch O-ring - BMW #13621743299
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