Strange Duty Cycle reading and Code 17 "O2 sensor grounded"?
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1990 Mercedes 190E
Strange Duty Cycle reading and Code 17 "O2 sensor grounded"?
This is my first query on this forum seeking assistance for my 1990 190E 2.6. The duty cycle reading at the X11 port is acting strange. The car starts and runs fine. With the ignition on and engine not running reading is at 69.9% so very close to the 70%. With engine running and cold the reading sits solidly at 49.9% so ideal as well. When engine reaches full operating temperature the reading begins to bounce around the 50% but then over a period o about 15 seconds the reading begins to drop until the it bottoms out aound 0-15%. My diagnostic tester shows a code "17" which is O2 sensor grounding. The wires are all intact and the Bosch O2 sensor is only about a year old. I suspect that the O2 sensor is the cause of the strange duty cycle readings when engine is hot. I have read on an online search that the 4 pin temperature sensor can be faulty and tricks the ECU to malfunction. I would appreciate any assistance forum members can provide. I am the the original owner of this 128,000 km. car which I bestowed on m grandson a few months ago but I still ike to help with the maintenance of the. car.
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190E 2.6L 1989, 190E 2.6L 1988, BMW 535dXdrive 2014, BMW 428i 2015
Hi Laura, I commented on the unrelated post but it seems your coolant temp sensor is fine. It is starting in open loop properly and after it heats up (I assume a little before 80c) the ECU goes into closed loop as expected. So that pretty much vindicates the coolant temp sensor and the ECU's reading of it.
I sure hope it is not an ECU malfunction again but this time with the O2 sensor circuit. You and your GS should try and pull up the carpet and attempt to measure the voltage.
I think you have done this before so I will not explain that part of it.
Remember the ground is any chassis ground you can find around, the door strike plate works.
I sure hope it is not an ECU malfunction again but this time with the O2 sensor circuit. You and your GS should try and pull up the carpet and attempt to measure the voltage.
I think you have done this before so I will not explain that part of it.
Remember the ground is any chassis ground you can find around, the door strike plate works.
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I tested the O2 sensor today. results as follows;
Engine fully warm and disconected from the ECU wire .44V
Connected to ECU with copper wire between contacts engine fully warm between .09 at idle and .75 bouncing rapidly at idle but went to .87 at 2500RPM
Duty Cycle still erratic and bouncing around quickly. It seems the O2 sensor isn't dead. When I checked the duty cycle with the sensor wire disconnected the meter sat at 50% which if I recall means no signal from O2 so the ECU seems to be getting something from the sensor and reacting even if nor what it should be.
X11 Error Code #17
I will try tomorrow to ground the O2 sensor with a clip to a solid ground and see how that works
Engine fully warm and disconected from the ECU wire .44V
Connected to ECU with copper wire between contacts engine fully warm between .09 at idle and .75 bouncing rapidly at idle but went to .87 at 2500RPM
Duty Cycle still erratic and bouncing around quickly. It seems the O2 sensor isn't dead. When I checked the duty cycle with the sensor wire disconnected the meter sat at 50% which if I recall means no signal from O2 so the ECU seems to be getting something from the sensor and reacting even if nor what it should be.
X11 Error Code #17
I will try tomorrow to ground the O2 sensor with a clip to a solid ground and see how that works
Last edited by LauraS; Sep 5, 2021 at 08:11 PM.
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My recollection is that it is supposed to cycle between 0.1V and 0.9V every second or two. I could be mistaken, as it has been 3-4 years since I last tested mine for no reason other than curiosity.
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Well perhaps my meter is not very accurate. In any event it does seem to vary within your approximate range e.g. 0.09 is only 0.01 shy of 0.1 etc.
Last edited by LauraS; Sep 5, 2021 at 07:59 PM.
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Yes that is pretty close to what I had observed. I wonder if the problem is intermittent in nature due to wiring issues.
You may need to hook up an EHA current meter again Laura and observe what it is doing during cold and in transition to the lambda control and beyond.
You may need to hook up an EHA current meter again Laura and observe what it is doing during cold and in transition to the lambda control and beyond.
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From: In the bush on the shores of Lake Nipigon
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I don't think it is intermitent. Apparently from my reading the code may indicate other issues buut the question is what are they. Maybe just learn to live with it as the car does start and run well. Curious to know though.
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190E 2.6L 1989, 190E 2.6L 1988, BMW 535dXdrive 2014, BMW 428i 2015
If you want to know the health of your emission components, it is best to observe the EHA current if there are no other obvious clues.
You have made a harness for that correct?
The fact that your duty cycle is railing to one side is not good at all. Not normal Laura.
You have made a harness for that correct?
The fact that your duty cycle is railing to one side is not good at all. Not normal Laura.
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From: In the bush on the shores of Lake Nipigon
1990 Mercedes 190E
I tested the EHA electrics yesterday before my grandson left for home. Ignition on engine not running +22.8mA
engine running cold +3.8
" " hot +13.3
Code Reader always returns to 17 flashes O2 sensor grounded etc.
Maybe another messed up ECU?
engine running cold +3.8
" " hot +13.3
Code Reader always returns to 17 flashes O2 sensor grounded etc.
Maybe another messed up ECU?
Last edited by LauraS; Sep 7, 2021 at 07:25 PM.
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There is definitely something wrong with the lambda loop. You emissions is being enriched in closed loop in a major way Laura.
The ECU was an ebay find if I recall correctly. It could be the ECU or the wiring or the O2 sensor. Let's think about some more diagnostic testing for the next time your GS returns.
Did you decode what the 50% static duty cycle mean. Is it the same? (O2 sensor shorted to ground?)
You still have the old ECU correct? I know it had the cold start problem but it was OK running hot, correct?
The ECU was an ebay find if I recall correctly. It could be the ECU or the wiring or the O2 sensor. Let's think about some more diagnostic testing for the next time your GS returns.
Did you decode what the 50% static duty cycle mean. Is it the same? (O2 sensor shorted to ground?)
You still have the old ECU correct? I know it had the cold start problem but it was OK running hot, correct?
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Laura, searching the web it seems the oxygen sensor fault code 17 is actually a misnomer for the problem.
It should just say "EHA current out of range" instead. Because that is what throws that code.
So now we have to find out what makes the EHA current go so high. I have seen posts with various causes.
Air leaks, EGR issues, coolant sensor issues, etc. etc.
It should just say "EHA current out of range" instead. Because that is what throws that code.
So now we have to find out what makes the EHA current go so high. I have seen posts with various causes.
Air leaks, EGR issues, coolant sensor issues, etc. etc.
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Thanks for doing the research on this. I have read that the 4 prong coolant sensor if defective can cause the code 17. The EGR valve was working the last time I checked it. Definitely the ECU is sending an enrichment signal. I know it isn't advisable but could the FD be running too lean and the ECU trying to compensate and would adjusting ito run richer be advisable? I am getting a Duty Cycle that is at the lower end bouncing between 0 and 30%. Yes the staic 50% indicates an inoperative O2 sensor but this isn't the case since it works and only sits at 50% until the engine reaches temperature. I did notice that the duty cycle didn't start bouncing until the engine temp gauge went past 80 C so maybe a temp sensor is reading low or the O2 heater is not working.
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1991 190E 2.3
Corrosion and or dirt in just one or all of the various connections to all of these parts can also cause these kinds of results. I would suggest making sure that everything is nice and clean at all of the various connecting points in the system before concluding that a particular part might be at fault. All it takes is one corroded or dirty connection to start putting bad information into the system that then does try to compensate for the original bad information.
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At this point Laura, we can not rule out anything. This could even be a more catastrophic early signs of fuel delivery issue involving fueling.
The first decision making branch point is the answer to this question:
Is the emissions system just responding properly to all the input it is receiving or not.
So you will need to determine if the emission system just reacting normally to a fueling issue.
Do you believe that the engine is running super rich after it warms up? Do you smell gas from the tailpipe?
The ECU is trying to enrich the mixture but it maybe just doing the right thing because the FD is not delivering the fuel the engine needs.
Maybe check the spark plugs (all of them for signs of super rich mixture).
I'm afraid you may have to re-connect your fuel pressure gauge for a quick check.
The first decision making branch point is the answer to this question:
Is the emissions system just responding properly to all the input it is receiving or not.
So you will need to determine if the emission system just reacting normally to a fueling issue.
Do you believe that the engine is running super rich after it warms up? Do you smell gas from the tailpipe?
The ECU is trying to enrich the mixture but it maybe just doing the right thing because the FD is not delivering the fuel the engine needs.
Maybe check the spark plugs (all of them for signs of super rich mixture).
I'm afraid you may have to re-connect your fuel pressure gauge for a quick check.
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I have an EGR valve and also a MAS unit in this car. reading up on the error code manual I see some codes can be read from the 16 pin diagnostic related to temperature sensor. I think that I need to do some more reading and checking when I can get the car here. The engine runs very good, clean exhaust and no sign of rich running. grandson says mileage is pretty good also. I am looking to buy another multi meter which has duty cycle. I just don't trust the old one that I have. I will keep you posted when I have the car in a fewdays. I may lend him my new Rav4, he would like that!
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The grandson called this afternoon. The car was running and starting not bad but when he when to start it after school it started but immediately died and was running poor but would run if he held the gas pedal down he says. I am at a loss but would an OP relay cause this? Too far away to go look until Saturday. I might have a spare that works.
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OVP relay? I doubt it. It was working fine when the car was at your place being checked out. I'm still leaning towards a serious Fuel Delivery issue here centered around either fuel pumps or FD itself. The last episode with your GS having to push down the gas pedal to keep it going may just be another sign of poor fuel delivery.
When he brings the car over perhaps check the spark plugs, if they look normal, I'm afraid we will need to look into the FD being the culprit.
When he brings the car over perhaps check the spark plugs, if they look normal, I'm afraid we will need to look into the FD being the culprit.
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A good suggestion to check the spark plugs for their condition, Dolucasi. Spark plug condition may certainly shed light on the problem. Since it looks like actual fuel delivery might be the issue, I would go even more basic and check the fuel filter and fuel lines to make sure there's no clogging going on there as that can cause all kinds of issues.
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I will look things over when I can see the car. I will get back on Monday with any news. I have my pressure gauges and meters to do some testing. Apparently and for no reason he had left the ignition on and forgot about it when he was visiting his girlfriend and when he came back to the car it would turn over but would no longer run properly hence my thoughts of it being the OVP>
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I can safely say it is not your OVP. If you are measuring current at the EHA, your ECU is powered up. Otherwise it will read zero current.
What I would do as a simple elimination is this.
When the car is back and after it reaches operating temp, disconnect the battery, swap in your old ECU with the cold start problem. Reconnect battery.
See if it behaves the same (meaning EHA railed to positive). If it does, your ECU is not the problem, swap your new one back in. Your ECU is not the culprit.
Then take some fuel pressure measurements again. And see what you have.
This would be my advice.
- Cheers!
What I would do as a simple elimination is this.
When the car is back and after it reaches operating temp, disconnect the battery, swap in your old ECU with the cold start problem. Reconnect battery.
See if it behaves the same (meaning EHA railed to positive). If it does, your ECU is not the problem, swap your new one back in. Your ECU is not the culprit.
Then take some fuel pressure measurements again. And see what you have.
This would be my advice.
- Cheers!
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OH MY! now another start problem. I brought the car back to my place. I found that the EGR valve was disconnected from the vacuum hose. Once connected car started and ran really nicely. EHA test showed when hot idle it was reading around 0.1mA. The Duty Cycle was reading funny but it was wandering over a narrow range. My MM is obviously broken since if plugged into X11 it would register in the 80%'s, unplug and try again and it was in the 0% and so on but at least it was reading in a narrow range not bouncing between 0 and 90% etc. as before. Eureka! problem solved......or so I gleefully thought. Went out this morning to drive it back to the G.Son and the car would fire then stall, fire then stall over and over and over. It will not start and run so now what? Fuel pump cycles and CSV fires so some fuel and some ignition. Time to begin all over. This is exactly what was happening last winter. So in the next while I will begin again to do all of the fuel and ignition tests. I will get back with results once I consult all of the posts on the BenzWorld site about the last time this happened. There are other things to do but this needs fixing and I dn't mind a challenge. Suggesstions welcomed.
Last edited by LauraS; Sep 13, 2021 at 08:36 PM.
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Just so I have this correctly Laura, what you found was that the hose that goes from the EGR switchover at the battery side firewall back to the intake was disconnected correct?
So now that is fixed and the hot running is fine but your cold start problem is back.
I wonder if you damaged something during the EHA current test? And now you are not getting the fuel enrichment during cold.
Can you please reconnect the EHA current meter and measure it one more time in this condition of no start.
So now that is fixed and the hot running is fine but your cold start problem is back.
I wonder if you damaged something during the EHA current test? And now you are not getting the fuel enrichment during cold.
Can you please reconnect the EHA current meter and measure it one more time in this condition of no start.
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I will check cold start EHA cold running enrichment tomorrow. Car started fine once hose you described was connected to EGR . So not only EGR open but vacuum leak so no wonder ECU sent rich signal to EHA. I did disconnect OVP to see what would happen and without it hooked uo even CSV doesn't see to work so likely not that anyway as you suggested. Be back tomorrow with results.
