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Getting intermittent SRS with code 9002 Control module n2/7
Hello all!
My wife's 2006 s500 is getting an intermittent SRS with code 9002 Control module n2/7. I get the code at random car startup. When the SRS light comes on, the 9002 code is stored. I got this code randomly during a 1 hour drive on the freeway, it went away after 15 mins. When the SRS light comes on, the car will not shift out of park. I have to shut off the car and restart.
Here's what the code says:
9002 Control module N2/7 ( restraint system control unit (circuit 15 R) no voltage present at circuit 15
Is there a faulty relay or something?
Thank you very much for the help. I thought it may be my battery, so i purchased a brand new AGM battery. (the old one started a bit slow, but still started everytime) The AGM is so much stronger.
with the new battery, I am still getting the intermittent SRS light.
Kevin
Circuit 15 is switched battery power. All power starts as circuit 30 - unswitched battery power, always hot. Somewhere, there will be a switch or a relay, or a computerized control unit that control whether there is power on the switched circuit, which becomes a 15 circuit at that point.. Your problem may be a poor connection on a 30 circuit, or on/in the switch/relay/control module fed by that 30 circuit, or in the 15 circuit.
There should be a fuse and relay chart rolled up and stored on the tool tray in the center of the spare wheel. You could start by pulling fuses and checking for any traces of corrosion or heating, then check the relays the same way. If you are very lucky, this might solve the problem.
One known problem with the W220 is a plugged drain valve in the HVAC plenum under the hood. Open the hood and find the large black plastic grille in the right rear corner. Remember that left/right is ALWAYS from the viewpoint of the seated operator, so the right rear corner will be on your left. Use a flashlight to look all the way down to the bottom of the funnel, and see if there is any trash or debris there. If the drain at the bottom gets plugged, rainwater or washwater can fill the funnel and drain into the the cockpit - the interior of the car. It will drain UNDER the carpet and insulation, and there will be no visible trace of water.
Once the water is inside the car, it will flow back thru the channels under the carpet, wetting the major "pre-fuses" located there. This will cause corrosion and electrical problems. The water will eventually make its way, again with no visible signs of water or moisture, all the way to the rear seat, where it will wet the fuses, relays and control modules located under the seat. Corrosion here will cause no end of strange electrical problems.
The only way to solve this water intrusion is to first, remove the small drain valve located in the plenum drain. Then you must remove the right front seat, and all of the right carpets and thoroughly dry the floor area, the insulation and sound deadening, and the carpet. It will take several days of drying! You must also disconnect the battery, then disassemble every electrical connection under there and thoroughly remove all traces of corrosion.
You can check the plenum for water, especially after a rain or wash. Then you can pull the right front carpet and insulation up and check for any traces of moisture. If there is moisture under the insulation, it will slowly destroy the electrical system under there.
Thanks Wally! It has been raining for a few days. Ill check the drain to see if it got clogged. its been a year since i cleaned. Also reseated some of the relays in the passenger side under the good (right side) ill pull some fuses to look for corrosion. but since i just reseated some relays, ill wait for it to come back. luckily after SRS light comes on, and I cannot shift into gear, turning off the car and restarting it fixes it... for now.
another symptom. The wipers don’t work. When I turn in the wiper, the pass airbag light comes one near the shifter.
Originally Posted by wallyp
Circuit 15 is switched battery power. All power starts as circuit 30 - unswitched battery power, always hot. Somewhere, there will be a switch or a relay, or a computerized control unit that control whether there is power on the switched circuit, which becomes a 15 circuit at that point.. Your problem may be a poor connection on a 30 circuit, or on/in the switch/relay/control module fed by that 30 circuit, or in the 15 circuit.
There should be a fuse and relay chart rolled up and stored on the tool tray in the center of the spare wheel. You could start by pulling fuses and checking for any traces of corrosion or heating, then check the relays the same way. If you are very lucky, this might solve the problem.
One known problem with the W220 is a plugged drain valve in the HVAC plenum under the hood. Open the hood and find the large black plastic grille in the right rear corner. Remember that left/right is ALWAYS from the viewpoint of the seated operator, so the right rear corner will be on your left. Use a flashlight to look all the way down to the bottom of the funnel, and see if there is any trash or debris there. If the drain at the bottom gets plugged, rainwater or washwater can fill the funnel and drain into the the cockpit - the interior of the car. It will drain UNDER the carpet and insulation, and there will be no visible trace of water.
Once the water is inside the car, it will flow back thru the channels under the carpet, wetting the major "pre-fuses" located there. This will cause corrosion and electrical problems. The water will eventually make its way, again with no visible signs of water or moisture, all the way to the rear seat, where it will wet the fuses, relays and control modules located under the seat. Corrosion here will cause no end of strange electrical problems.
The only way to solve this water intrusion is to first, remove the small drain valve located in the plenum drain. Then you must remove the right front seat, and all of the right carpets and thoroughly dry the floor area, the insulation and sound deadening, and the carpet. It will take several days of drying! You must also disconnect the battery, then disassemble every electrical connection under there and thoroughly remove all traces of corrosion.
You can check the plenum for water, especially after a rain or wash. Then you can pull the right front carpet and insulation up and check for any traces of moisture. If there is moisture under the insulation, it will slowly destroy the electrical system under there.
Were you guys able to find a resolution for this? I looked around and all looks good, but I get this warning half the time. It won't let me shift out of park. My wipers are also completely dead no matter if the SRS warning is showing or not.
I wish I had a fuse chart for this car. Mine is missing 😔
Hi Nishboo.
The culprit was a faulty ignition switch. turns our that the accessory and/or run terminal inside the igntion switch (sometimes called the EIS) had carbon buildup. this caused an intermittent low voltage for the accessory or ignition wire. There is a video on youtube that shows you a guy diagnosing this and repairing.
I ended up repairing mine. I removed the EIS (the module you stick you key in) and disassembled it. I had to de-solder a few things. there is a metal contact that moves when turning the key. it had carbon on it. I bent a piece of tiny sand paper (after disasembling by desoldering) and cleaned off the carbon.. I also bent the contact for a more positive contact.
All is good now. I purchased a whole new SAM, disasembled the wipers to try manually, checked numerous other things, before i found the video on youtube of a guy diagnosing the same problem. you get the SRS light because there is low voltage going to the control unit, due to a bad contact in ignition switch... maybe hope it helops
you can test this if you had a star comp. just check the input voltage of the suspect failed control unit.
another way to test is, next time you see the failure, jiggle the ignition key kind of violetly to dislodge some carbon... if it works, then you know it's the culprit.
you can test this if you had a star comp. just check the input voltage of the suspect failed control unit.
another way to test is, next time you see the failure, jiggle the ignition key kind of violetly to dislodge some carbon... if it works, then you know it's the culprit.
I have Star. Would I be looking at Airbag? How would I check wipers?
go to the airbag module and note the voltage of the module. have you tried the key-jiggle test? if you jiggle the while in the on position and everything works, then its prob the EIS.
[QUOTE=wallyp;8298998]Circuit 15 is switched battery power. All power starts as circuit 30 - unswitched battery power, always hot. Somewhere, there will be a switch or a relay, or a computerized control unit that control whether there is power on the switched circuit, which becomes a 15 circuit at that point.. Your problem may be a poor connection on a 30 circuit, or on/in the switch/relay/control module fed by that 30 circuit, or in the 15 circuit.
There should be a fuse and relay chart rolled up and stored on the tool tray in the center of the spare wheel. You could start by pulling fuses and checking for any traces of corrosion or heating, then check the relays the same way. If you are very lucky, this might solve the problem.
Hi everybody, I saw WallyP's answer here on the forum, I have a similar problem with a Mercedes Benz B class - I removed the passenger seat without disconnecting the minus battery terminal and drove the car. My freind used his scanner to read and reset some codes, but im now left with9111 Control unit N2/7 Restraint system control unit defective. I visited a Mercedes independent who said the unit needed to be replaced at a total cost of 1200 Euros... I approached a UK and a Company in the states who specialize in resetting / flashing the SRS unit so they can be reinstalled. But both companies said they couldn't fix a 9111 code unit. I heave spent weeks and weeks searhing for an answer on the net with no success and find no reference to a 9111 code. Wally P seemed very knowledgeable in this thread and I wondered if anybody had insight into whether i can try anything before taking this hugley expensive next step.
many thanks Paul
Circuit 15 is switched battery power. All power starts as circuit 30 - unswitched battery power, always hot. Somewhere, there will be a switch or a relay, or a computerized control unit that control whether there is power on the switched circuit, which becomes a 15 circuit at that point.. Your problem may be a poor connection on a 30 circuit, or on/in the switch/relay/control module fed by that 30 circuit, or in the 15 circuit.
There should be a fuse and relay chart rolled up and stored on the tool tray in the center of the spare wheel. You could start by pulling fuses and checking for any traces of corrosion or heating, then check the relays the same way. If you are very lucky, this might solve the problem.
Originally Posted by wallyp
Hi everybody, I saw WallyP's answer here on the forum, I have a similar problem with a Mercedes Benz B class - I removed the passenger seat without disconnecting the minus battery terminal and drove the car. My freind used his scanner to read and reset some codes, but im now left with9111 Control unit N2/7 Restraint system control unit defective. I visited a Mercedes independent who said the unit needed to be replaced at a total cost of 1200 Euros... I approached a UK and a Company in the states who specialize in resetting / flashing the SRS unit so they can be reinstalled. But both companies said they couldn't fix a 9111 code unit. I heave spent weeks and weeks searhing for an answer on the net with no success and find no reference to a 9111 code. Wally P seemed very knowledgeable in this thread and I wondered if anybody had insight into whether i can try anything before taking this hugley expensive next step.
many thanks Paul
read my quote... could be the ignition switch. easy to test, as i had posted. if it is the igntion switch, you will see other failures like the wipers, since i think that draws significant power from the ignition circuit.
Circuit 15 is switched battery power. All power starts as circuit 30 - unswitched battery power, always hot. Somewhere, there will be a switch or a relay, or a computerized control unit that control whether there is power on the switched circuit, which becomes a 15 circuit at that point.. Your problem may be a poor connection on a 30 circuit, or on/in the switch/relay/control module fed by that 30 circuit, or in the 15 circuit.
There should be a fuse and relay chart rolled up and stored on the tool tray in the center of the spare wheel. You could start by pulling fuses and checking for any traces of corrosion or heating, then check the relays the same way. If you are very lucky, this might solve the problem.
Originally Posted by wallyp
Hi everybody, I saw WallyP's answer here on the forum, I have a similar problem with a Mercedes Benz B class - I removed the passenger seat without disconnecting the minus battery terminal and drove the car. My freind used his scanner to read and reset some codes, but im now left with9111 Control unit N2/7 Restraint system control unit defective. I visited a Mercedes independent who said the unit needed to be replaced at a total cost of 1200 Euros... I approached a UK and a Company in the states who specialize in resetting / flashing the SRS unit so they can be reinstalled. But both companies said they couldn't fix a 9111 code unit. I heave spent weeks and weeks searhing for an answer on the net with no success and find no reference to a 9111 code. Wally P seemed very knowledgeable in this thread and I wondered if anybody had insight into whether i can try anything before taking this hugley expensive next step.
many thanks Paul
hello,
You fix the problem?I have same problem with my B class car and same error code but no solution to fix
This thread saved me hours of troubleshooting (my 2006 S500 exhibited the SRS error, wipers not working, and shifter stuck in park issues, all intermittently.) After disassembling the shifter and discovering it was fine (no broken part preventing me from shifting out of park) I dug deeper and discovered this thread tying together all of my intermittent symptoms. I thought I would give back to the great community here by uploading some photos of my ignition module showing how to take it apart to get at the contacts that needed cleaning.
After you pry apart and remove the plastic ignition module case...
Desolder these three pins on top side Desolder these three pins on bottom side The board now pops right off the key cylinder mechanism These are the contacts you need to clean. I used 2000 grit sandpaper, followed by printer paper to clean off any dust, and then a drop of Deoxit to keep things sparkly
I hope the above photos are helpful! You do need either a desolder station (which I have) or a solder sucker or some copper desoldering braid and solid desoldering skills to free the board from the cylinder mech.
Good luck!
-Pete
Last edited by Petebacher; Sep 12, 2023 at 04:50 PM.
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hope it helops
