1990 300te Code 3 on Pin 14
 

Not getting any hits on another thread, so I will re-post here:

1990 300te
California Car, 147,000 miles, 124.090 body, engine 103.983

Ok, I built Arthur's home brew code reader as a project with my 10-yr old son. It came out great and works like a charm. Tested the car, found tons of codes (most are probably old), cleared them one at a time and then drove some errands.

Upon return I got the following:

Pin 3 - 17 Oxygen sensor is shorted to positive or ground
Pin 14 - 3 TN/TD signal (RPM) interrupted

I have 2 questions:
Is pin 3 picking up the same Oxygen sensor fault that I get when I use the built-in diagnostic unit on my car that reports on the emission system?

What does the message on the Pin 14 fault mean?

Thanks in advance.

Pin 3 addresses the same DM as the built-in Led for Cal versions.
Pin 14 is a TN signal glitch...try coearing it again and then see if you get a singler Flash on that module..if you do, them clear the memory on that one.

Arthur, thanks for the reply.

Yes, I was able to clear the Pin 14, fault code 3 with the code reader. Now a single flash on that pin. I will test drive tomorrow and report back with findings.

So what is a TN signal glitch anyway?

After 10 minute test drive, 3 flashes on pin 14 has returned.

What is it and how to correct?

Shameless bump.

Anybody know what this error code means and how to correct?

Pin 14 - 3 "TN/TD signal (RPM) interrupted"

Did you do the Memory clear I posted?????????????

Yes.

I got 3 flashes, held button down for 8 secs, there was a click and a single flash. Then key off.

To test I keyed on and held for 2-3 secs and got a single flash.

I assume that meant that all was clear on pin 14.

You have only cleared the codes. I need you to clear the MEMORY .


After single flash [ which signifies Fault CODES cleared ], wait 2 secs , hold for 5/6 secs , turn key OFF for 50 secs , On for 10 secs , Start car.
That clears any glitch in the MEMORY.

If the code then comes back , you have an engine speed signal fault and can address it then . If not , you are OK w/memory reset.

I have done as you instructed. After starting the car, I show just one flash on all the pins. I will test drive tomorrow and report further results.

One question though; I did this procedure tapped into pin 14. Would this need to repeated to clear the memory on each code or does one time wipe all codes out? (just in case for the future)

Each module is reset individually and none can be reset until a single flash confirms there are no codes stored.
I had you do that one b/c that is where you are having a problem and I will not get out test procedures and schematics until I know your Memory has been reset b/c it could be a simple memory glitch ..that's all.

Arthur,

After test drive today, fault 3 on pin 14 has returned. I cleared the code and then cleared the memory per your instructions. When I turned off the car, I checked and the code 3 was still there.

To be sure, I repeated this two more times. Same result. Now what?

Ok

Having a litle trouble finding info on that chassis b/c it is MAS controller Cal version w/16 pin diagnostic box. Kinda rare combo.

But , I did find TN signal code and I would first check this sensor and the wires from/to it.. and take fuse #7 out and clean the ends and the holder.. [ or spin the fuse a few times in the holder]

http://catalog.peachparts.com/RenderScriptTemplate.epc?_cmd=epccat_VehicleAAA&cookieID=2GN17VPXQ2GN17XWT3&yearid=1990%40%401990&ma keid=MB%40%40MB%40%40X&modelid=300%2DTE%2D001%40%40300TE+Wagon&catid=F%40%40Engine+Electrical&mode=P A&subcatid=F6010@@Reference+Sensor&source=www.peachparts.com&clientid=catalog.mercedesshop

Fuses have all been recently cleaned.

Do you know which sensor this error code covers? (or both)
What is the procedure to check the signal from these sensors?

What is the source of documentation to troubleshoot these codes? ( I have all of the MB paper manuals and the MB WIS software)

I have noticed that since I tried to clear the memory today, the car is behaving differently. Before it turned over immediately. Now it takes longer to start and I have to give it gas. The idle seems very weak.

I don't have info on that model w/cal version.

I believe the front is speed sensor and the rear is crank sensor.
That info should be in your docs somewhere.

I will check my MB manuals.

Bottom line, if I forgo any testing/troubleshooting and just replace both sensors, will the issue be resolved?

Any sense on why my idle has changed after doing the memory clear procedure?

You seem to have an intermittant problem and each sensor can be checked with a scope or you can ohm meter each. If you are having a start/running problem, it would more likely be the Crank sensor . Look at your WIS under CPS tetsing.
Does the tach work?
You may also just have to run the car a few days b/c after a memory clear , the car management has to relearn . That takes some driving.

Do you see a CPS code anywhere on the 8 module?

Car management has to re-learn? I didn't know they were that sophisticated in 1990. I will check my WIS under CPS testing. The tach works perfectly. With an ohmmeter, am I just checking for contuinity on each wire looking for breaks?

I am not sure I understand your question about a CPS code on the 8 module. If you are referring to pin 8, I only have readouts on pins 3,6,7 & 14. Except for the push button and LED, all other pins are blank.

Ok .. Pin 8 would be Ign module on later models w/16 pin DM
So, yours will be Pin 3.
Like I said , I just can't find any info on that Cal version , mostly b/c it was early Cal w/16 pin...so I do not know what they have . I did find codes for that chassis, but Not Cal. Emmssions.
But I do have TN codes on Fed versions and you can ohm the sensors from the end of the cable and see if your WIS gives you those values..you can also flex the cable/harness and watch the meter for intermittant readings, indicating poorconnection/wiring.
The AllData just has "Check speed sensor wiring" as test for TN code. They also have a scope pattern test at ECU, but that does not help you. [ unless you have a DSO?]
I will do some more searching, but that is an early Cal car and info is hard to find...Your WIS would prob have more info than my AllData does.

According to the documentation that I have, Pin (socket) 3 is for the Continuous Fuel Injection System (CFI) and as you indicated earlier addresses the same DM as the built-in LED for Cal versions. I suspected this earlier since the flashing light on the home-made reader flashed in sync with the built-in LED while my yellow wire was in this socket.

I now have 2 codes present on that socket: 17 "Oxygen sensor is shorted to positive or ground" , and as of yesterday 18 "Current to idle control valve is illogical".

The code 17 is the same one that I had about 2 years ago. Replaced Oxy sensor, tested all wiring, then someone on this group suggested checking the Duty Cycle. Made adjustments to that and the code has been gone since then. About 1 month ago my CE light came on and Code 17 returned. That is what got me motivated to build the code reader and get everything tested and fixed.

Code 18 is new since I erased the memory yesterday and started having the idle trouble.

That could be 02 sensor sig, duty cycle, or even OVP relay . Tap that relay and see if any change and check the fuse on top..I would even pull it and see what the socket and pins look like. That is power feed for ICV

Thanks for the input. OVP was replaced within the last 18 months. Big weekend planned with USC-Ohio State game in town. I will test on Monday and report findings.

Well, you may just want to pull the rug and check those 02 sensor wire connections under the rug there ....the code is telling you an open or shorted 02 sensor, so it could be right at the plug from footwear..I have seen that happen in cars with a lot of passenger traffic.
You should also have 12v there for 02 heater.

I will certainly check the O2 wires again. When I did so 2 years ago, they were perfect and the sensor was performing within spec. Still had the Code 17 though. The code finally went away when I adjusted the duty cycle.

Can the idle control valve be damaged by clearing the memory on the diagnostic module?

I only ask because the idle trouble and Code 18 started after doing so. Will the idle issue be corrected and the code disappear after the car rmanagement re-learns?

No. or at least I doubt it. I just can't find any info on that chassis b/c it was in between on the diagnostics and emmssions mandates, being early cal.

The reason I had you try the relearn is that being an early 16 pin CAL system , it may have had adaptations, but if it did not, then trying the Memory clear procedure would just do nothing b/c there would be nothng in there to address. If there was no memory, you would just be redoing the code clear procedure. I think , as you do, that memory came a couple of yeares later w/HFM and LH 12 pin.
That car has MAS Controller according to my info , so I am unsure on this point.
I would not rule out the 02 sensor as that is where things are pointing. Duty could also be the problem, being out of 02 range. And OVP is feed for duty, so is there a feed problem there ..???
I would look at 02 first...

Recap: 1990 300te California car, 148k mi.

I pulled the OVP and checked its fuses and connections. All good. Was replaced July 2006 at 120,000 mi.

Since clearing, the code 18 on socket 3 has not come back.

Pulled the rug and all wires to O2 sensor test good.

After all testing outlined below, Code 3 on socket 14 returns (TN/TD signal (RPM) interrupted). I have ordered both speed sensors and will install later this week.

Car stalls upon hard braking. Stalled on a freeway offramp this weekend. I put it in nuetral, and restarted while coasting. This problem has now happened about 10 times in the last 4 months.

I share your concern of the O2 sensor/duty cycle. After I clear code 17 on socket 3, the CE light goes out but returns immediately after re-start along with code 17. With the Sears multimeter I get a duty cycle reading of 81.36%in KOEOff mode. I know from past experience that I should get the 85% CA reading.

When O2 sensor warms up, the duty cycle starts and ranges from 37-46% at idle. O2 sensor stabilizes at a reading of .17 volts. If I increase the RPM to 1500, the duty cycle defaults back to a fixed 81.36, but then kicks back in after about 30 sec, and displays in the range of 73% (O2 signal then jumps to .8v). Increase to 2500 RPM and the duty cycle defaults back to fixed 81.36 for 30 seconds and then displays in the range of 120% (O2 signal still at .8v)

The O2 sensor appears to be functioning correctly according to the Landis article (.2 to .8v). My understanding is that if the mixture is rich it will read above .7v, lean below below .3v).

My duty cycle is totally wacked. I hesitate to start adjusting when I can't even get the 85% baseline CA reading. What do you make of my getting readings of 73-120% at 1500-2500 RPM?

Man, do I feel stupid.
I accidently had hit the HOLD button on my Sears Duty Cycle meter and that's why it was displaying 81.36% in KOEOff mode. Also, output signal type must be set to %. Now it reads 50% in KOEOff mode (perfect).

When Arthur had me clear the memory to reset Code 17 in socket 3, it must have reset my duty cycle as well since after I corrected the buttons on the meter, my duty cycle was about 80% (way to lean). Turned the set screw CW and now it runs between 45-50% on idle (perfect). Only problem is that at 2000 rpm, duty cycle is 65-71%. Spec calls for it not to vary by more than 10%. Is this cause for concern, and how to correct?

Issue # 2: (Original problem)
I also just replaced my front speed sensor and my rear crank sensor. Still getting the code 3 TN/TD signal (RPM) interrupted on socket 14. It comes back immediately even after clearing the code and clearing the memory of the module. Any ideas on how to correct this code?