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I just got my Launch Creader Elite Benz, and first use I'm quite happy with how well it works.
my wife's 2016 E350 4Matic wagon has been throwing an error on the dashboard for a few weeks now, that the SRS System is disabled.
The Launch says, its SRS N2/10 code B273513 "The squib for pyrofuse "On-board electric line" has a malfunction, there is an open circuit"
googling suggests this 'pyrofuse' is on the main battery plus lead, and is designed to go off if there's an airbag event, to disable all electrics in the car. The error suggests its a wiring iissue with the triggering squib, so when I have the time (wife has car on errands now), I'll dig farther. I already found and spliced one rat-chomped wire pair near the battery... maybe my crimped splice sucks, and I need to do it over with solder and shrinkwrap
LCG, great you've done almost the whole job but your Santa-Cruz rat had a serious appetite for more Benz wiring.
Keep the heatshrink option on the table for now. Have you tried to match wiring colors to SRS diagram?
I haven't yet. catch22 is often my wife is gone much of the day with the car, combined with all the rainy weather of late, minimizes my opportunities to look at it. hoping to get under the hood tomorrow afternoon.
and indeed, the chewed wire pair IS the squib wires to the pyrofuse on the battery positive terminal, white-green and violet-blue... Now I need to find my soldering stuff, its been a couple years.... k, found.
took apart my original crimp repair, soldered and double shrinkwrap, and clear the fault, and its STILL throwing the same fault, and if I read the live data, it says its open circuit. grrrrrrr. These squib wires go directly to N2/10, the SRS control unit, which I believe is behind the lower center dash, forward of the ashtray.
now I'm stymied.
Last edited by Left Coast Geek; 01-21-2023 at 03:18 PM.
and indeed, the chewed wire pair IS the squib wires to the pyrofuse on the battery positive terminal, white-green and violet-blue... Now I need to find my soldering stuff, its been a couple years.... k, found.
took apart my original crimp repair, soldered and double shrinkwrap, and clear the fault, and its STILL throwing the same fault, and if I read the live data, it says its open circuit. grrrrrrr. These squib wires go directly to N2/10, the SRS control unit, which I believe is behind the lower center dash, forward of the ashtray.
now I'm stymied.
Another great step towards a complete fix.
A rat chewed the pyrofuse wiring pair. It's now reliably patched but same SRS fault keeps coming back.
> What could the rat do:
A - Not only opened but shorted wires together?
B- I do not think rat disconnecting pyrofuse control could kill pyrofuse circuit with it still conducting normally. So if harness is testing fixed with continuity, the next issue is inside SRS controller.
> What style circuitry:
- Fixed steady +12 through a fuse or micro trace
- Switched GND through 10¢ power MOSFET.
> Meaning of Fault :
The SRS is not seing +12v show up on the switched side coming through the pyrofuse back into SRS.
> What to do next?
If wiring has continuity, now focus on SRS box...
1- Test the harness supply side for missing power. You can do this right at pyrofuse terminals.
2- Invite yourself inside N2/10 for a visual inspection. Disconnect batteries!
You're right about SRS being located behind ashtray.
This is when pieces start flying out.
🤞
Last edited by CaliBenzDriver; 01-21-2023 at 05:31 PM.
a squib is pretty low resistance, and I can't really picture a short doing any damage with the residual level of current they would be using as a continuity test.
there's no connector on the Pyrofuse side, and I shrink-wrapped my splice, so it won't be easy to 'ohm' it out. I probably should have tested things before I spliced it.
I have zero desire to go spelunking in the center console of the car to find N2/10 in order to do any tests from that end.
a squib is pretty low resistance, and I can't really picture a short doing any damage with the residual level of current they would be using as a continuity test.
there's no connector on the Pyrofuse side, and I shrink-wrapped my splice, so it won't be easy to 'ohm' it out. I probably should have tested things before I spliced it.
I have zero desire to go spelunking in the center console of the car to find N2/10 in order to do any tests from that end.
Yeah, I too believe pyrofuse is as good as new.
Getting the astray sliding doors gismo out, I think will provide some form of access to SRS.
These modules are not frequently worked on, supplier knew better than to use solderless connectors. They are located in the safest location.
and I thought it could help finding out if the problem is at the battery terminal side (saving work under the dash). However, I am not an expert on this matters and I rely on @CaliBenzDriver for advice for this type of things. So, Cali you are next (again)
and I thought it could help finding out if the problem is at the battery terminal side (saving work under the dash). However, I am not an expert on this matters and I rely on @CaliBenzDriver for advice for this type of things. So, Cali you are next (again)
"Pre-facelift" cars have their pyrofuse integrated into their prefuse box.
The facelifted cars have a prefuse cover to plug the missing pyrofuse hole.
The good thing about these pyrofuses is they have no way to blow up like airbags... "safe" to work around.
Last edited by CaliBenzDriver; 01-22-2023 at 03:18 AM.
ah, no, I don't have another scanner, but that thread sounded like he was having problems with the ICARsoft thing. I have the new Launch Creader Elite Benz/Sprinter..
but yes, when playing with this one, it threw a few phantom codes, somethiug about outer left front radar (wtf, I ain't got no radar?!?). It seems to work better if I turn the car on without starting the engine before beginning a scan cycle.
anyways, gonna check that blue-yellow plug on the Pyrofuse tomorrow... too dark and cold now. Thats exactly what mine looks like. I gently poked/wiggled at that blue-yellow thing when I was in there this morning, but didn't realize it was a plug.
Last edited by Left Coast Geek; 01-22-2023 at 02:02 AM.
I see you really want to unplug your pyro pigtail... to work the plug out, you want to first first release the orange locking pin on top.
What to expect on that twisted lineset?
> I think a fixed GND with a gated DC12V anytime you wish pyro fuse to say sayo-nara
> or a full time 12V line plus a switched GND control.
Plan-B : poke through splice work....
> Give the wife's car another beautiful splice job
> peel/remove outer insulation
> poke at each individual line without short-circuiting them.... what do you get?
Last edited by CaliBenzDriver; 01-22-2023 at 09:50 PM.
in addition to whatever it is that fires off the pyro, its also monitored, which means they are running a small current through it to detect its connectivity.
thats the older style, where the pyrofuse is on the prefuse box, under the postive battery terminal used for jumpstarting and charging. my pyrofuse is directly on the battery
I am not expert on this; however, from what I read the two thin wires connector with the orange plug, the squib, is monitored as you mentioned. The module expects a resistance around 3Ohm.
Does the squib feels tight to the terminal? Is it making "very good contact"? Could it be that while splicing the cable something else got loose around there?
Say I were to cut the wires, and measure the resistance of the squib, I would expect 3 Ohm: otherwise the squib is faulty. If you get 3 ohm, then the issue is upstream, i.e. the splice is not providing the right resistance from the module to the squib. It cannot be lower since it is in series; therefore too high resistance.
Reminder, I am electrically challenged , so take with a grain of salt.
the plug and the wires into the plug feel very snug and secure. but I didn't realize that orange cap on the side is a locking pin, so I'll look at that tomorrow.
Only way I'm going to be able to ohm the squib is to either disconnect my splice or unplug that connector.
This is the expected value by Xentry, all under 3 Ohms if possible. I now, sometimes do not trust Xentry Specified Value 100% anymore as I have seen it is placing kinda generic data for many models, granted for some components only.
01-20-2023, 06:58 PM
