Monitor not ready

Tiny
KARLENWEBSTER
  • MEMBER
  • 2002 MERCEDES BENZ C320
  • 3.2L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 144,513 MILES
Took emissions test for the fourth time monitors reading not ready for catalytic converter, oxygen and, now its secondary air.
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Wednesday, March 22nd, 2017 AT 7:53 AM

11 Replies

Tiny
STEVE W.
  • EXPERT
You need to drive specific drive cycles to get the monitors to run. BUT you may want to have the car scanned with a MB specific scan tool. There are trouble codes that can be set that do not light the check engine light but can prevent some tests from running as well.

The three items you mention are ones that should run very rapidly.
Here is a somewhat generic drive cycle as an example

Begin with a cold start (coolant temperature below 122 degrees F and the coolant and air temperature sensors within 11 degrees of one another). This condition can be achieved by allowing the vehicle to sit overnight, and then by beginning the drive cycle the next day. Most drive cycles will be difficult to follow exactly under normal driving conditions, so the driver should exercise caution, road safety, and courtesy to others.
* Start the engine. Idle the engine in drive for two and a half minutes with the A/C and rear defroster on.
* Turn the A/C and rear defrost off, and accelerate to 55 mph at half throttle.
* Hold at a steady speed of 55 mph for three minutes.
* Decelerate (coast down) to 20 mph without braking or depressing the clutch.
* Accelerate back to 55 to 60 mph at throttle.
* Hold at a steady speed of 55 to 60 mph for five minutes.
* Decelerate (coast down) to a stop without braking.

Repeat all but the cold start twice.
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Wednesday, March 22nd, 2017 AT 11:43 AM
Tiny
KARLENWEBSTER
  • MEMBER
Did the drive cycle twice, secondary air completed bt O2 n catalyst sensor hasn't complete to ready. Drove thecar the following day n still nothing, my question do I need to replace all sensors. Or the car battery?
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Monday, March 27th, 2017 AT 7:55 AM
Tiny
STEVE W.
  • EXPERT
Usually not a sensor issue BUT there are items that can cause issues with the monitors setting. To see those you need to have a good scan tool to see which items are specific to that vehicle.
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Monday, March 27th, 2017 AT 8:27 AM
Tiny
KARLENWEBSTER
  • MEMBER
Took car mb for answer they came up with replacing ignition coil for cylinder#2 and all spark plugs which was done also changed air filters under car hood still the sensors not ready
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Monday, March 27th, 2017 AT 10:02 AM
Tiny
KEN
  • ADMIN
Hello,

I think Steve W has come on the something, if the thermostat is stuck open and the does not get up to operating temperature the monitors will not run. I would check the thermostat to see if it is stuck open and go from there.

Please run this test and get back to us so we can continue helping you.

Best, Ken
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Thursday, March 30th, 2017 AT 10:48 AM
Tiny
KARLENWEBSTER
  • MEMBER
Hello I had the thermostat checked and replaced this morning 03/31/2017 drove car for a couple of hours now my question is do I need to do a drive cycle to see if the sensors read ready n if they don't set what do I need to do next?
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Friday, March 31st, 2017 AT 12:44 PM
Tiny
KEN
  • ADMIN
You need to drive it for a couple of days before the monitors will set. About 50 miles.

Please let us know
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Friday, March 31st, 2017 AT 5:52 PM
Tiny
KARLENWEBSTER
  • MEMBER
Drove car today 51 miles south and 51 bac south and monitors havnt complete to ready, cataylst converter was checked technician said it was ok at this point im lost on this vehicle I do nit understand what the ussue is need more advice to go on.
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Saturday, April 1st, 2017 AT 7:53 AM
Tiny
KEN
  • ADMIN
Sometime it can take a while, just keep driving it to see what happens, couple more days of regular driving.
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Saturday, April 1st, 2017 AT 4:15 PM
Tiny
STEVE W.
  • EXPERT
There are specific drive cycle items that have to be perfect for the various monitors to run. For instance the O2 sensors may not run the monitor tests if there is a small exhaust leak, or there is a slow sensor.

The problem is that Mercedes does not provide the exact parameters for those tests to run.
If you take it to a MB dealer and have them hook it to the factory specific scan tool and then look up the drive cycle information and what has to be set for the monitors to run you might have better luck. It's very possible that some tiny item, like fuel level, exterior air temperature or another data bit is stopping them from running.

In your case I doubt that the catalyst monitor will run because the system cannot get the O2 sensor monitor to run. The O2 won't likely run because the secondary air hasn't run. So you need to have whatever testing and repairs done to get that system to work first.
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Sunday, April 2nd, 2017 AT 1:26 AM
Tiny
KARLENWEBSTER
  • MEMBER
Hi I purchased a obdlink for my vechicle im not sure if im reading it correctly or quite understands whats goin on but on my phone under the obdlink app I check for messages it says a broken pipe nand stated that the commanded secondary air/off )what does that mean?
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Sunday, April 2nd, 2017 AT 10:08 AM

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