Have been having a reoccurring P0170/P0173 (P2017/P2086) in my '01 SLK320 (same chassis/drivetrain as Crossfire). Have been told that when in a long hot idle (takes about 150 minutes) the Secondary Air Injection is supposed to come on and correct a long slow move from a near zero STFT in both banks to +25 (Torque Pro) which trips the codes. Has been mentioned that the Secondary Air Injection i(SAI) is supposed to come on to correct this. Mine is only coming on when cold and not when hot (added a LED to tell when on).
Have replaced MAF (Bosch, 2x), O2 sensors (2x), plugs. No vacuum leaks, gas cap good, all rubber excellent.
People here seem more technically knowledgeable than other foums & need local (Central Florida) help if possible..
Have also been told that something the the ECU ID indicated it is corrupt. Is this true?

If I need a new ECU my only option is the 5 speed automatic transmission. Does anyone know/have ? I've exhausted my capabilities.
Control unit ME-SFI 2.8
MB number 030 545 60 32
Supplier Bosch
Hardware status 08/00
Software status 15/00
Diagnosis identifier 1/1
Version(internal) M112_0305456032_E4
Tester identification(Variant 93026700 coding)

 

150 minutes on idle?

 

You either have an air leak or you are lacking fuel. Secondary inj is not the issue.

 

You either have an air leak or you are lacking fuel. Secondary inj is not the issue.

 

Sorry, it takes about 15 minutes.
Fisrt one (1501) had been running about five minutes arleady. SAI is off for all.







.

 

What is the fuel pressure doing during the fifteen minutes? Put a pressure gauge on the rail and watch the pressure. Could be as the regulator gets heat soaked it is dropping pressure. and the ECU is trying to compensate by adding fuel. Also check the MAF readings, at 2500 rpm no load should be about 9 ~ 12 grams/second and then on the road WOT should go up to about 90grams/sec.

 

What you were told about the secondary air pump coming on after long slow idle doesn't make sense to me. Adding air to the exhaust increases burning and heat which the O2 sensor interprets as a lean condition (excess oxygen), giving low voltage to the PCM/ECU and thus the PCM will increase short term fuel trim. Thus adding more oxygen to an already lean condition as noted by the short fuel trim is the wrong thing to do. IF I INTERPRET THIS CORRECTLY!
If the 02 sensors are operating correctly and the PCM is responding correctly giving you the increase in short term fuel trim the voltages the 02 sensors are producing should be 0 to no more than .5 volts. Checking the voltages of the O2 sensors against the short term fuel trim could help you determine if the PCM is going bad as you suspect.

 

Good idea, I'll check. Have a good fuel pressure gauge. May be a day or two since rarely leave the house.

I agree, have been getting mixed and conflicting information all along. Only thing I am sure of is that long slow increase in the fuel trim at idle in gear only. Am "assuming" that as the STFT increases positive it means the ECM is adding fuel to correct a lean condition. At least that is my interpretation of "Self-adaptation of mixture formation for right (and left) bank of cylinders is at limit value (at idle speed). Enrichment over permissible limit"

 

I know we spoke earlier, I've had time to read over your codes and test, while it's possible my previous suggestion of swapping O2 connections might still be the fix I think you might have a vacuum leak here. I have seen the oil cap in the past cause the short term fuel trims to rise only at idle. Oil caps are like $7 at the parts store.

 

Thank you, will check. Manifold vacuum is very stable at about 16.2 +/- .1 in hg @ 550 rpm. Idle is smooth except when cold. Personally I wold expect a vacuum leak to move faster to stabiity and not have a 15-20 minutes steady slow increase in STFT for both banks. What should low idle manifold vacuum be ?

 

33.9 mbar

 

1 in-hg ? I am seeing 16.2 +-.1 in hg in gear at 550 rpm and 18.1 in Park at 700.

 

And just found the secondary O2 sensors were swapped (Bank 1 is US passenger side rite ?). Reversed and STFT is much more stable. Had one surge right after leaving grocery but may have been something left over. Thanks to Dual for the idea. BTW Fuel Pressure is steady at 58 psi.

 

Way to go DualSportDad with the downstream sensor info. Thank you for that info!

 

If you caught what I originally posted before my edit, you're welcome. I mistook his P code for another that I had seen recently. I think he has a vacuum leak at idle and it seems like he has checked all his bases, I remember having a oil cap kick my *** one time and I believe it was for a similar or possibly exact issue. Turns out his O2 sensors were plugged in backwards , once the vacuum leak was fixed he would have started getting codes for O2 sensor delay and unknown subfault. If you have my original post saved before my edit, feel free to post it, it will explain the slow response and unknown subfault codes.

 

That's the spec I have. Have you ran down the actual diagnostic chart from Chrysler for this code?

 

On one of my n/a crossfires I have a aftermarket secondary air pump that is pretty loud and I can tell you it most certainly does come on at times during idle after the engine is hot. Iwill try and find the time to brush up on the secondary air system this weekend in case this is the issue that is causing his CEL.

Edit: when the pump comes on at idle after the engine is hot (sitting at a stop light) I'd say I have never heard the pump run for more than 2-3 seconds, if that helps at all.

 

Re-post of edited DualSportDad;

know we spoke briefly earlier but this thread is lacking some information that I'm sure some will find helpful.

Downstream O2 sensors seem to be known as having their only duty to be monitoring the efficiency of a cat converter. While this is a main function it also has a function that allows it to protect the cat and prolong its life. It does this by setting a goal voltage for the upstream O2 sensor. That goal voltage is the target a/f at closed loop. In this case the vehicle is is trying to achieve that goal then when it comes to idle it takes some sort of equation and compares the current upstream O2 data to the downstream O2 data to verify the current goal voltage being set by the downstream is the correct value.

If the engine is running smooth, no poor idle and no flat spots during acceleration then you can usually narrow it down to the converter area. I have seen small pin holes in a cat cause these codes and what is much more common, down stream O2 sensors plugged into the wrong banks. It is possible that the ECU is performing the equation incorrectly but that is a last resort repair as that is impossible to know for sure. To me it sounds like your O2 sensors are plugged into the wrong banks because you have not mentioned any driveability problems. I have seen people gut cats and then install spark plug non-foulers into the down stream O2 sensors to get the down stream O2 out of the exhaust enough to keep the check engine light off for having no cat. While it keeps the light off it changes the upstream goal voltage to a point the vehicle runs pretty bad. Even a pin hole in a cat can have this affect. But if the O2 sensors are plugged into a fairly healthy engine with cats that are working properly but in the wrong banks it will still well enough but fail the test the ecu performs because it's likely one cat is worn more than the other and there is a very narrow margin for the spec the ECU is looking for.

Good luck, hopefully swapping the connectors for the down stream o2's solves all your woes with the car.
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Does this reference voltage "goal voltage" function of the downstream sensor only occur during closed loop?

 

I get the secondary pump coming on briefly after driving the car and then coming to a stop at idle as a short shot of fresh cool (relative) air into the exhaust could help cool the manifold. But, wouldn't injecting air into the exhaust any longer than that cause the O2 sensor to signal a lean condition and increase fuel when it is not necessary? Padgett was idling for fifteen minutes. Could the secondary pump find the increase in exhaust temperature over that 15 minute time frame and think it is time to turn on for a couple seconds? or longer?

 

OK. Have almost thrown the kitchen since at it now, just switched the oil filler cap for a new one. Only time I have seein anything other than P0170/P0173 (2017/2086) has been an occasional "pending" P0410 that never sets.
Keep in mind this is an early '00 SLK320 (same driveline as Crossfire just prefer a retractable to a soft top) so the ECU progam may not do everything a later car can. I have checked out the whole SAI system and is good/clean but only see it active when cold, never when warmed up. That might be a later revision.

The sudden spike at the grocery store I have to wonder if part of a learning process since when back down and has not repeated.

Posting here because of my coupe (no problems or codes) and people here are more technical tham the MB forums. Dual was the first to mention the swapped sensors. Have not seen screwy clong term cycles since.

Photo is of momentary spike (enough to set both codes) at the grocery store within a minute of starting and in Park (slightly higher idle and better manifold vacuum). Bright sunlight is not good to photograph a display. but is legible.