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Discussion Starter #1 (Edited)
JAL, you have good information and research sources, so I'm asking you first.
question- I started getting an intermittent code 22, oxygen sensor heater circuit G3/3, for drivers side bank of cylinders.
it causes the car to drop out of closed loop, into open loop, after going for a ride, coming home pulling in driveway,
then letting it sit there and idle and cool off.
monitoring it with the Snap On 2500 scan tool, the o2 sensor for that bank, will suddenly stop transmitting while sitting there idling,
and go into open loop, fixed voltage 450mv.
is there a fuse or relay for that circuit ? or fusible link ? there must be some sort of protection somewhere in the design.
if so, where is it ? does anyone have a schematic or diagram of the circuit ?
o2 sensors are both new. switched them and they both transmit.
it's something in the car, wiring, or ?
switched EGAS modules, problems stays on same side.
while driving the exhaust naturally heats up and puts that side into closed loop.
but it can't maintain it while idling, it cools off and drops into open loop.
heater circuit is needed to maintain closed loop.
anyone else had this problem ? it would be great if it was a simple fuse or relay, easy to change.
rather than pulling up the rug and tracing the o2 sensor harness. ouch.
it started out as a low o2 sensor reading around 50mv steady,
then it progressed into a heater circuit code. no check engine light.
plugs were changed to factory spec Bosch non-resistor, F8DC4
i highly recommend the nonresistor plugs to everyone, they burn spotlessly clean- no fouling- hotter spark visibly when tested outside the engine.
anyone have ideas on the code 22 ? o2 heater circuit problems are annoying
 

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No fuses or relays, just the connector on the side of the tunnel. The connector is easy to access from inside the car
Run the seat all the way back, and pull the front section of carpet where it overlaps the rear at the side of the tunnel from under the lip of the console. The connector should be staring you in the face. There's no need to remove the carpet from the car.

The hot side of the heater goes to pin 9 of the LH module N3/2. The ground for the heater goes to the ground point behind the glove box insert, above and to the right side of the HVAC pneumatic control block.

I'd pull that LH module, and see if the pin on the connector is pushed back or corroded. Check continuity between it and the pin on the connector on the side of the tunnel. See if it's got high resistance or a short to ground. Should be the yellow/white wire at pin 2 of the tunnel connector.

I wouldn't think the heater would have any effect once the car is warmed up, unless it's getting shorted out and affecting the LH module.
 

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BTW, I assume you exchanged the LH modules since there is only one EGAS.
If you exchange them for any length of time, you should reset the fuel trims in both, drive the car for awhile, and let them readapt. I know STAR can reset them. Don't know about the Snap-on.
 

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Discussion Starter #4 (Edited)
my error and misnomer, YES I switched the LH modules, to see if problem moved to other side. it did not, it stayed on right side. moving o2 sensors side to side, the right side o2 was cooler to the touch than left side. left side was HOT would burn your hand without a glove. I switched the LH modules back again, because yes I could see the adaptive history on each was different in the snap-on tool, based on where it was located.

it's a relief that connector is so easy to get at. ground behind glovebox, can I access it from the floor of the passenger front seat looking up behind dash and glovebox ?? or remove glovebox insert ? or ??

pin 9 on LH module, are they numbered, or do I need a pinout diagram of the plugins ??

correct, driving the car both banks are in closed loop, varying o2 voltage output signal from 50mv to 900mv as they should. upon returning home, it sits only a few minutes idling in driveway, the right side bank then goes cold, down to 450mv on the o2, and stays there, i.e. back into open loop on passenger side right bank only. drivers side left bank stays in closed loop. coolant temps for both sides remaining the same.

I'm going to change the 4 pin coolant temp sensors, both sides, being they're cheap enough.

will pull rug and check it out...stay tuned, thank you again.
 

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The pins are numbered both on the module and the connectors in the coffin box.

When you reinsert the modules, be sure they are fully seated in the connectors and the box. Use the heel of your hand and pound them in, or a rubber mallet.

To get to the ground, pull the insert from the glovebox after removing 4 push in plastic fasteners, two at front top and two at the front bottom of the insert. With a little effort and some plastic trim tools, it pulls out from the front. Be careful, and remove the wire connectors at the glovebox light as you remove the insert.

Jon
 

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Discussion Starter #6
ok JAL, here is status- I pulled up rug, found connector, haven't done any checks yet.
pulled both LH modules, pin #9 on each is good, no corrosion or bent pins.
removed glovebox insert- yes it can be done without removing door, by pulling 4 plastic pins-
but I don't see the ground wire. will look again tomorrow - to the right of the vacuum control box with all the small vacuum lines on it, and above ? is it attached with a screw or bolt to a vertical surface, or horizontal surface ?
will return tomorrow with a bright penlight to try to find it.
my gut tells me it's the connector in floor corroded...from the inside it looks new,
I'm going to remove the female socket plug from the floor, and take a good look at it
 

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Discussion Starter #9
on my 1994, the cluster of brown wire grounds, is behind the right side kick panel, on the passenger side footwell/floor area, right side vertical outer wall.
I could not find anything behind the glovebox insert.
I read some of the Startek info pages you sent me, and it said ground, found in "right side footwell" or "passenger side footwell". so I pulled that lower right side kickpanel off, it comes out easily, and there they were, all connnected to one stud, along with a bunch of other connectors, vacuums hoses, etc.
haven't traced anything
 

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Discussion Starter #10
The hot side of the heater goes to pin 9 of the LH module N3/2. The ground for the heater goes to the ground point behind the glove box insert, above and to the right side of the HVAC pneumatic control block.
JAL- when I removed the glovebox insert, I could not get to the area where you said this ground was. The right side HVAC heater ductwork is in the way. Is there an easy way to remove it ? I don't want to break it trying to get it out of there. but I'm curious if there is another cluster of grounds where you said there is.
 

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You have to remove the air outlet on the right side of the dash. There is a narrow plastic piece in front of the dash speaker grill that pops out. Under that is a screw. Remove that with a right angle screwdriver. Then you can carefully remove the speaker grill. Under that are screws that hold the air outlet in place. Remove them. There are also tabs inside the outlet that have to be released. Often, the airduct you refer to comes out with the outlet. If it doesn't, just pull it out.

If your car has sat in heat it's whole life, the plastic of the bits can be extremely brittle. Be careful.

This video starting at about 4:10 shows the process. Bookmark the series as they show how to remove the entire dash, console, and HVAC.

Jon
 

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Discussion Starter #13 (Edited)
great video chain, he made 8 video segments, I went forward to part 5, it shows everything back there behind glovebox

if you go to time point 2:28 in this video of his, you can see what I mean

there is something back there but can't make it out clearly.

if it's the ground wire that's bad, the best thing to do in this situation, is cut it at the sensor plug socket, and run my own ground wire to the lower ground stud behind footwell side kick panel, and just let the other one dangle. this way I can avoid taking that heater duct out. if the heater duct comes out easy, then I'll proceed to that back ground stud area, if it is there.

 

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Discussion Starter #14
the problem is the o2 sensor. to review- the left side o2 was intermittent for this heater circuit problem, code 22, after pulling left side kick panel, finding ONE brown ground wire that someone had put a new eyelet on, the eyelet was loose. I could pull the wire in/out of it. recrimped that wire, still no o2 function. yesterday I put car on ramps, unplugged the o2 sensor, and pulled up the rug, and unbolted the o2 sensor socket from the floor. checked the ground circuit pin, it was now good for continuity. started the car with the o2 unplugged, probed the o2 socket plug for heater pin circuit voltage, when the car hit the proper temperature, heater feed pin had 14 volts DC.

being there is 14 volts to the socket heater circuit feed, and the heater circuit ground wire pin is also grounded and good, it can only be the o2 sensor. a new one is on the way, ordered it 2 days ago. what must have happened, the loose ground over past several months, must have drawn more amperage, from the bad connection, and burned out the heater in circuit in the o2 sensor.

that long bolt that holds the left side kick panel on, was a bitch to remove. had to hammer a flat blade screwdriver into the phillips head, to get enough bite to get it to turn, and had to chisel at it just to get it to initially break free. it was seized solid.

once again most of the problems with this car, and with all cars I work on, is what previous hack job mechanics have done, half assed repairs that snowball into worse problems.
they did not use the proper size eyelet, the wire being too small to be crimped in the large hole in the eyelet, left if loose in there. I had to use vice grips and really bear down on it, to get it to crush and crimp tightly.
IMG_20190916_140724.jpg
IMG_20190921_150005.jpg
 

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Discussion Starter #15
new o2 sensor installed left side, engine is now transmitting from both sensors, varying o2 signal from 50-900mv.
completely changed the character of the car again. now it has an even more stable idle from the time it's started,
until I shut it off 20 minutes later, after taking it for a ride.
lots of power in 1st-2nd gears. I haven't opened it up on the highway yet, just back roads up to maybe 60 mph.
next job is the exhaust system. that will be yet another thread !
it's been 6 months wrenching on this car, off and on, weather and time permitting.
but it's getting there. thanks JAL, other moderators, everyone else for your help and tech tips.
after finally getting the o2 sensors to both work and the idle mixtures correct,
I changed the oil today to 10-30 synthetic amsoil. the car loves it.
it sounds great albeit little exhaust leaks throughout entire exhaust system.
it takes 12 quarts as you all probably know. I bought gallon jugs.
after draining the oil, replacing filter, and oil drain plug,
added 2 gallons. there was still nothing on the stick !
thirst little devil. it took all of 3 full gallons jugs.
that's $115 worth of amsoil. but money well spent.
 
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