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View Full Version : ASSYST reset cause a check engine light?


Sacto John
03-05-2013, 02:28 AM
I did my routine oil change this Saturday on my 06 T1N, and today (Monday) when I reset my ASSYST service indicator my check engine light came on, and I mean as soon as the Van beeped and reset the engine light came on.

I am going to have a local shop run the codes but I thought that it was extremely odd that the reset would cause the van to throw a code, especially since it has never done this before.

Anyone else have this happen?

autostaretx
03-05-2013, 02:44 AM
Did you check your dipstick today? (remembering to have the engine hot, or accept that it's going to look 1/2 quart low if cold)
Did some connect get knocked loose? (such as the nearby Intake Air Temp sensor)
Does your ScanGauge show any weird numbers? (such as an unbelievable IAT)

--dick (who has reset his Wrench many times...)

Sacto John
03-05-2013, 03:00 PM
Did you check your dipstick today? (remembering to have the engine hot, or accept that it's going to look 1/2 quart low if cold)
Did some connect get knocked loose? (such as the nearby Intake Air Temp sensor)
Does your ScanGauge show any weird numbers? (such as an unbelievable IAT)

--dick (who has reset his Wrench many times...)

I will check my connections and oil level. I do not have a scan gauge, so I can not check any of the codes myself, and I have no idea what IAT is.

Aqua Puttana
03-05-2013, 03:33 PM
I will check my connections and oil level. I do not have a scan gauge, so I can not check any of the codes myself, and I have no idea what IAT is.

Intake Air Temperature.

Most any auto parts supply houses will scan your ECM for codes (engine related only) for free with a generic scan tool. Don't let them do a reset though because there may be other Sprinter specific codes which cannot be seen and then they may be lost. vic

surlyoldbill
03-05-2013, 03:55 PM
There are some free or cheap iProduct or Android phone apps that can scan for codes (bluetooth OBD device needed, $30 Amazon/Ebay).
My CEL came on after unplugging the MAF while running (to check turbo activation while diagnosing a problem). It has not turned itself off yet, I have no LHM (limp home mode) problems, the van runs normally.
I think I read that if the IAT is messed up, the van will enter LHM, not allowing speeds over 2000rpm.

Sacto John
03-05-2013, 04:17 PM
Good information, but I am still puzzled why I would have no code then as soon as I reset the ASSYST I get a code

surlyoldbill
03-05-2013, 06:23 PM
Have you tried resetting again to see if it would go away?
Computers sometimes require a re-boot if they initialize wrong.

Sacto John
03-05-2013, 07:14 PM
Have you tried resetting again to see if it would go away?
Computers sometimes require a re-boot if they initialize wrong.

That was the first thing I tried. :)

Anyway had a friend at a local (Non-Mercedes) shop pull the code for me. The code that came up is 671. anyone know what that code is for?

autostaretx
03-05-2013, 08:30 PM
The code that came up is 671.
Unfortunately, that's not the entire code.
It should start with a letter (P for Powertrain, B for body, etc)
and be 4 digits (or characters) after the letter.
I'll assume it's really P0671, which translates to:
Cylinder 1 Glow Plug Circuit

So you could have a glow plug that's drifted out of its desired resistance range.

But... to a "real" Sprinter scan tool, the Glow Plug #1 codes are:
P2133-GLOW PLUG #1 CIRCUIT EXCESSIVE CURRENT
P2133-GLOW PLUG #1 CIRCUIT OPEN CIRCUIT
P2133-GLOW PLUG #1 CIRCUIT SHORT TO GROUND
P2133-GLOW PLUG #1 CIRCUIT SHORT TO VOLTAGE

...the P0671 is a "generic" code (used by emission testers)

--dick

Sacto John
03-05-2013, 09:15 PM
Unfortunately, that's not the entire code.
It should start with a letter (P for Powertrain, B for body, etc)
and be 4 digits (or characters) after the letter.
I'll assume it's really P0671, which translates to:
Cylinder 1 Glow Plug Circuit

So you could have a glow plug that's drifted out of its desired resistance range.

But... to a "real" Sprinter scan tool, the Glow Plug #1 codes are:
P2133-GLOW PLUG #1 CIRCUIT EXCESSIVE CURRENT
P2133-GLOW PLUG #1 CIRCUIT OPEN CIRCUIT
P2133-GLOW PLUG #1 CIRCUIT SHORT TO GROUND
P2133-GLOW PLUG #1 CIRCUIT SHORT TO VOLTAGE

...the P0671 is a "generic" code (used by emission testers)

--dick

PO671 Is the full code that I was given.

Is it possible that when I reset my ASSYST that I caused the glow plug "drift" out of its desired resistance range? I did have to try to reset it 3 or 4 times before I got it to reset. Could turning the key to its #2 position (turning the glow plugs on) and the off again then on again in quick succession have freaked out the computer?

I may just reset the codes and see if I throw the code again before I get too worried about it, the van has been running great.

Aqua Puttana
03-05-2013, 09:32 PM
I see you live in sunny California.


My experience is that if it is not cold enough for the glow plugs to be called upon to do their job, the glow plug codes go into hibernation. My guess would be that by tickling the ASSYST reset you awakened the ECM and it spit out the glow plug code which had been hibernating.

The MIL light should go out on its own after the proper number of start, up to operating temperature, not needing glow plug assistance, and restart cycles.

I wouldn't worry too much about it. Unlike the NCV3 engines which need the glow plugs for DPF re-generation, the T1N basically only needs glow plugs when it is colder than about 32F.

FWIW. vic

autostaretx
03-05-2013, 11:58 PM
Is it possible that when I reset my ASSYST that I caused the glow plug "drift" out of its desired resistance range? I did have to try to reset it 3 or 4 times before I got it to reset. Could turning the key to its #2 position (turning the glow plugs on) and the off again then on again in quick succession have freaked out the computer?
Does flicking the light switch of a 5-bulb chandelier cause a bulb to burn out? Sometimes (especially if one of the bulbs is weak).
You won't have "freaked out" the computer, but the current surges may have made it warn you that it's seeing something odd.
As Vic/Aqua says, just ignoring it and driving for a few days may make the CEL (check engine light) go out...
If the ECM doesn't get a repeat report from the glow plug module (which has its own computer) for 3 to 5 start/run/stop cycles, it will turn off the light (but remember the code).

Here's the glow plug circuit from the 2006 Service manual. (http://aie-services-2.net/Sprinter/) The zig-zaggy lines in the Glow Plug Module are resistors (or the fuses), the little triangles are "comparator" circuits.
The beefy relay that actually turns ON the plugs are those two switched contacts on the left of the module.

50917

You turn on the key... the relay pulls in and the contacts close. Current flows through the individual resistors to their plugs.
The comparators monitor the voltage drop across those resistors.
Too low a voltage drop (usually) means that the plug is "open" or showing growing internal resistance.
Too high a voltage drop (usually) means that the plug is "shorted", or dropping in resistance.
The Glow Plug Module "knows" the plugs' resistance-versus-temperature "curve" (they have lower resistance when cold).
Flicking it on and off may simply make the number one plug (now hot) appear to have too high a resistance than the GPM thinks would be appropriate for a "cold" plug. That could trigger the light.
The GPM talks to the ECM via the single wire at the bottom... probably short pulses (think: "morse code") ... your on/off flicking could've accidentally generated a signal that the ECM mis-interpreted as a glow plug fault code.
The pulsed current rush could've blown plug one's resistor, too (this is what surlyoldbill's glow plug module repair fixes). Life happens.

Since you're in Florida, you usually don't need the plugs... you could measure plug one's resistance (it should be between 3 and 5 ohms), and/or compare it to the adjacent plugs. You could measure the voltage and current through that loop, again comparing to the adjacent plugs.

--dick

Aqua Puttana
03-06-2013, 02:17 AM
...Flicking it on and off may simply make the number one plug (now hot) appear to have too high a resistance than the GPM thinks would be appropriate for a "cold" plug. That could trigger the light.
...

--dick
That theory may be correct, but I've needed to try the key on - off, button push, hope for the beep, curse, try again... beat the windshield dance because it doesn't always work the first time multiple times, and I've never seen an MIL turn on.

It will be interesting to have the information from either a dealership level scan tool or a glow plug ohmmeter/12 volt fused source short test.

I suspect that there may be a glow plug fault that isn't being revealed in sunny California. That is a guess until we have more concrete information to give more direction.

vic

Added.
The procedure below works. Setting to the wrench(es) display before turn the ignition is a critical step.

I used the pause on the video and now noticed that the steps are:

1.)*With key off Press the miles button (that you use to get the trip odometer) until you see one or two wrenches. it is two quick presses to get to the Service Clock wrenches.

2.) * Remaining on the Service Clock/Wrenches, Switch to Ignition Position 2 "On"

3.) * Press "Miles" x 2 quickly.

4.) * Switch Ignition "Off".

5.) * Immediately Press & Hold In "Miles" button.
Keep held in.

6.) * Switch Ignition back "on".

7.) * Holding "Miles" button in - Should now hear "Beep".

8.) * Clock now reset.

Dick,
I think you're correct, but initially you need to start with the "Service Clock" displayed. After that they were probably just going back to it for video purposes. :idunno:

Anyway, I never intentionally started with the "Service Clock" displayed so I think that explains the randomness of my reset success. :doh: vic

Sacto John
03-06-2013, 02:34 AM
Thanks guys, all this information is great!

My check engine light did go off when I left work this afternoon, we will see if the light comes back on.

Even though I live in "sunny" California, I still have to start my van in temps below 32F 20-30 times a year, because of my fishing/hunting/camping addiction. Last month there was a span of two weeks where it was below 32F in the morning when I left for work, so if it is a glow plug issue I am sure it will show back up sooner or later.

Sacto John
03-06-2013, 10:43 PM
Light is back on...guess I will take the van to the Dealership and have it all checked out