Code P2258 Intermittent EML Secondary Air Pump

[BTank88]

Recently been getting this EML and subsequent error code come up, intermittent possibly only on cold starts.

P2258 Secondary Air Injection System Control A Circuit High

I'd guess the auxiliary air pump is not activating intermittently causing the EML and code on cold starts.

I'd like to start with basics first, and being an intermittent fault which upon clearing will stay away for several starts, I'm suspecting a relay of some sort. Lo and behold the circuit and pump is controlled by a relay upon researching:

Fuse Box Diagram Mercedes-Benz C-Class (W204; 2008-2014)

Fuse box diagram (location and assignment of electrical fuses and relays) for Mercedes-Benz C-Class (C180, C200, C220, C250, C300, C350, C63) (W204; 2008, 2009, 2010, 2011, 2012, 2013, 2014).

fuse-box.info

P	Valid for engine 156, 272, 276: Secondary air injection relay

Just trying to chase down the part number for it so I can source a replacement.

 

[whitenemesis]

Had similar on my CLS, turned out to be a dodgy connection in the plug at the pump

 

[BTank88]

Replaced the fuse, will report back if it's fixed or not.

Cleared the code and first start was OK but obviously will need a few cold starts before I can say it's been fixed.

I must say.. it's not like the air pump is extremely obvious when it's on. Is there a certain routine that it follows when it should come on or not? I had iCarSoft plugged on an was monitoring the pump status, and on the cold start it said ON for a couple of seconds then it went OFF and stayed off, but no EML was triggered that time.

Even on other starts, I can't say for sure if I've heard it or not.

 

[BTank88]

Ok, relay replaced.

The first start after the relay change was OK, no EML.

The second start after a few days, I got the EML, with a different code from iCarSoft:

1065 - Secondary air valve 1 has a short circuit to positive.

I had a good nosey around the engine bay, and first of all I couldn't see the actual pump anywhere. Anybody have an idea where it is?
Secondly, I think I see where the secondary air valve is, and everything seemed normal at least in terms of connections.

I'll keep monitoring over several cold starts, to see if errors are consistent. It would also help me if there is a way to manually trigger the secondary air injection system.. seems there is no way to do it via iCarSoft so I only get one chance a day really, I'm not sure if it turns on via consecutive cranks.

 

[BTank88]

Before I started it today, I had a good nose around the engine bay, I kid you not I must be blind but I can't see the pump from the engine bay. I can see where the fat hose goes near the passenger side front bumper area somewhere, but I can't see the pump. I can't see me having any sight of it unless I remove the undertray from below and look up into the bumper, or remove the bumper entirely. There is no sight of it through the front bumper views are blocked.

So, I started it today to see if error is reproduced (codes were cleared last cold start).

First I started monitoring on my diagnostic tool 'commanded secondary air injection status'. I wanted to compare if I could hear the pump compared to the air injection command from the car.

Right after starting it, I saw the status go to ON (UPS??) for about 1 second, then went to off again. No EML, no lights or any pump noises. I guess the car didn't want the system on this time, even though it was a cold start.

Then did another crank and this time status didn't change from OFF at all.

How on earth am I supposed to diagnose this thing if it doesn't even consistently get command from the ECU??

 

[BTank88]

Another cold start after the above, I got the EML and the original code in the topic again, but I didn't have my tool connected at the time so I didn't know what the commanded secondary air value was saying.

It would be so much easier if there was a way to trigger this system myself.. anyone got any ideas?

 

[Jobsworth]

Pump is located in the bumper void, in front of the nearside front wheel. Easy to bench test

 

[Jobsworth]

If you had a blown fuse it’s quite likely the air pump is toast. When you find it have a close sniff. Burned ones smell…. well, burned.

 

[BTank88]

Pump is located in the bumper void, in front of the nearside front wheel. Easy to bench test

How is it accessible? I can't see it from the top of the engine bay at all.

If you had a blown fuse it’s quite likely the air pump is toast. When you find it have a close sniff. Burned ones smell…. well, burned.

All I have done is replaced the relay for the system, I haven't checked the fuse of the pump. I will check this.

 

[Jobsworth]

Remove the arch liner piece that blanks the bumper void. You’ll find it.

On the w203 AMG’s it used to be common for the relay to stick and the pump to continue running till it overheated and died. I haven’t seen that with the w204, but it’s a similar arrangement

 

[KillerHERTZ]

Check out my latest video (also in the HOWTO section of this forum) where I show you replacing the secondary Air Pump Switchover Valve

Slightly different error codes, but for the same parts.

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[BTank88]

Tried some more starts, I saw DTC's being stored but without EML being on. It's possible the EML is only lit after a certain amount of DTC's are stored maybe.

Anyway, I want to be as sure as possible before I start replacing things. I really can't hear the pump running to be honest and it's looking more and more likely. I can only remember hearing it once a few starts ago, although it was not very obvious and it only seemed on for a few seconds.

I took out the switchover valve today and inspected it, looks fine nothing out of the ordinary.

P2258 Secondary Air Injection System Control A Circuit High
1065 - Secondary air valve 1 has a short circuit to positive.

I may start with the switchover valve first as it's a lot easier to get to, and then if no luck will start investigating the pump.

 

[BTank88]

Replaced the secondary air valve 1, switch over valve, whatever you want to call it today.

After replacement, the DTC still returned on a cold start. After having a further snoop around the engine bay.. there's another valve that was hidden under the cover. So I replaced this one with the old one, and fingers crossed next cold start I don't get any errors.

 

[BTank88]

That hasn't worked, I may have to look at the pump next.

I am conflicted though why the code is talking about the secondary air valve and not the pump which I'm sure has its own code.

Is there a fuse related to the valves themselves? I have checked the fuse for the whole system which is 40a and seems ok.

 

[BTank88]

Decided to test the pump first before blindly removing and replacing it.

I shorted the relay connections first in the fuse box, and the pump turned on. Surely this would rule out a pump issue. Relay itself is new, so the system must be capable of getting power. Fuses will be OK too.

I then started it cold, and sure enough the code came straight back.
1065 - Secondary air valve 1 has a short circuit to positive.

Now while I was nosing around in the engine bay, maybe about 1 or 2 minutes AFTER starting the car, I heard the pump switch on and I'm sure I heard the switchover valves click, can't tell if it was both but definitely heard at least one. The pump started at moderate speed then soon after went quite loud for about 10 seconds, and then stopped. But it sounded all normal and healthy. I didn't hear any hissing or air leaks that were obvious.

I'm gobsmacked now, it must be some kind of control input somewhere but no idea what it could be. Also this check seems to happen before the pump itself turns on, straight after starting cold, so the check must be done on engine start.

Another thing that is baffling me is that the code states 'secondary air valve'. The secondary air valves are the big metal vacuum valve I believe, but this is passive/vacuum controlled so how could this report a DTC? I don't see any electrical connectors on them either.

I do have the secondary cats removed, I wonder if the problem had started after this? Is there anything around that area that could trigger this problem?

 

[Jobsworth]

I think you need to check the wiring from the control valves back to source next. Can’t tell you from where I currently am, but it could well be the signal for them comes from the engine ecu

 

[BTank88]

I think you need to check the wiring from the control valves back to source next. Can’t tell you from where I cu isrrently am, but it could well be the signal for them comes from the engine ecu

Did a little more digging today. Only a small portion of the harness is visible, as it goes under the intakes and then around the back of the engine somewhere and I think it comes out the engine ECU area.

I traced the harness as much as I could and honestly couldn't find anything odd anywhere.

I did some more troubleshooting, this time I disconnected both air switchover valves, to see how the DTC's would react and see at least which one was causing the short circuit error.

This was interesting, after cold starting with both disconnected, I got a new error code for each:

Secondary valve 1 has an electrical fault!
Secondary valve 2 has an electrical fault!

Which leads me to believe both harnesses are at least live as it's detecting disconnection of the valves. It's also worth noting, the pump did not come on at all for this duration of a few minutes with both valves disconnected.

I then connected the left hand side one (I don't know which valve is 1 or 2 yet relating to the error codes). As soon as I connected, the pump came on and did it's thing for about 5 seconds. It's obvious that connecting the valve let the system activate.

The Secondary valve 1 has an electrical fault! also changed from current to historic, so now we know that it's definitely the left hand side valve that is number 1.

I also got another code for the other side:
I can't remember exactly but the code was, but it was something to do with secondary air flow not being sufficient in bank 2. Expected, as valve 2 was still disconnected, yet the system had started already.

So from all of this.. I feel the system is fully functional, but some small control is interfering with it somewhere. No idea what this could be. We know the harnesses are working as system is reacting to changes to it, and know the pumps functional. Relay is new. Valve 1 is also new.

There is one thing I want to try next, which was an observation from my last test. When I was waiting for the system to activate after cold starting, the system actually came on as soon as I started fiddling with the valve 1 electrical connector. I thought this was a coincidence, but maybe it wasn't I wonder if it is a bad connection on this side. I will try this tomorrow.

 

[BTank88]

Ok.. I think I'm pretty much out of ideas now.

I got the multimeter out today to measure and monitor voltages. I measured in both switchover valve harnesses. Consistent behaviour in both, ~8.4v at ignition on on each side, and goes to 0v a minute or two at ignition off. I didn't bother measuring the voltage at engine on, or when the system is active. I'm confident the power levels and the system itself is OK, especially considering the plethora of codes I got when I disconnected the valves in the earlier test.

Once again, a couple of minutes after cold start, I heard the pump kick in. This time I was monitoring on the iCarSoft the pump and valve status. From what I remember, the pump turned on first, then one valve was activated for a few seconds, then pump went faster, then second valve, then pump went really fast, and then after a few seconds everything turned off. I can hear the exhaust note change also when it activates.

I would hope this is normal operation, maybe someone could compare with their C63 if the cold start sequence is similar? It would be useful to know if we have to wait a couple of mins after engine start to hear the pump, or if it starts straight away on other cars. Every information document I read seems to stay pump stays on for a minute or two, mine only stays on for several seconds.

I haven't vacuum tested the metal valves, I do have a vacuum tester kit I wonder if this is worth doing or if it could cause my symptoms. Only 19k though on my car, but who knows.

The one thing that is completely consistent, is that the DTC get's raised on a cold start, pretty much straight away after engine start. I have never seen it appear again on subsequent starts, even if I turn it off after a short start and turn it on again.

 

[BTank88]

If I remove secondary air valve 1, I get codes for both valves 1 and 2 (electrical fault).

If I remove only secondary air valve 2, I get no codes for electrical fault.

Both connectors for valve 1 and 2 are giving 8-12v

Does sound like a short somewhere between the 2 valves.

 

[Jobsworth]

Hmm. Have you rung the cables back to the ecu? Sounds like one maybe running through the other in series