airbag throwing code 18, no DTC, dash switch not illuminating
03-30-2015, 09:58 AM
#1
Member
Thread Starter
airbag throwing code 18, no DTC, dash switch not illuminating
This weekend I installed a new head unit and also ran a Bussmann Add-a-Fuse to a switched USB plug block for phone charging. After reassembly, the airbag light is flashing a code 18.
I checked all the fuses that have anything to do with the airbags, and they're confirmed good (passed continuity checks with a DMM).
I checked the connection to the radio bezel, and it's solid. The connector itself is outputting ~11.4v when the key is turned, but the switch light isn't illuminating. The switch itself failed a continuity check, but I don't know if that's all the unusual with a combo switch/light.
I'm pretty sure it's the switch part, that in doing all the dash work I messed it up somehow. It has some really fine wiring in it, from looking at it.
So can someone confirm a code 18 will be fixed with a new switch? Searching either says yes it does or descends into TSB technical talk that I can't decipher. thanks!
I checked all the fuses that have anything to do with the airbags, and they're confirmed good (passed continuity checks with a DMM).
I checked the connection to the radio bezel, and it's solid. The connector itself is outputting ~11.4v when the key is turned, but the switch light isn't illuminating. The switch itself failed a continuity check, but I don't know if that's all the unusual with a combo switch/light.
I'm pretty sure it's the switch part, that in doing all the dash work I messed it up somehow. It has some really fine wiring in it, from looking at it.
So can someone confirm a code 18 will be fixed with a new switch? Searching either says yes it does or descends into TSB technical talk that I can't decipher. thanks!
03-30-2015, 10:26 AM
#2
Moderator (Ret.)
For code 18, I found this:
Since you had the center radio bezel off to replace the radio, I'd also check the upper center connector; maybe you bent a pin on its bulb when you reconnected it. Check the bulb's continuity with an ohm meter.
https://www.f150forum.com/f4/air-bag-...s-42-a-155660/
12=Low Battery Voltage
13=Air Bag Circuit Shorted to Ground
14=Primary Crash Sensor Circuit Shorted to Ground
21=Safing Sensor Not Mounted to Vehicle Properly
22=Safing Sensor Output Shorted to Battery Voltage
23=Safing Sensor Circuit Input Feed/Return Circuit Open
24=Safing Sensor Output Feed/Return Circuit Open
32=Driver Side Air Bag Circuit High Resistance or Open
33=Passenger Side Air Bag Circuit High Resistance or Open
34=Driver Side Air Bag Circuit Low Resistance or Shorted
35=Passenger Side Air Bag Circuit Low Resistance or Shorted
41=RH Primary Crash Sensor Feed/Return Circuit Open
42=LH Primary Crash Sensor Feed/Return Circuit Open
44=RH Primary Crash Sensor Not Mounted to Vehicle Properly
45=LH Primary Crash Sensor Not Mounted to Vehicle Properly
51=Air Bag Diagnostic Monitor Internal Thermal FuseFuse Blown Due to Intermittent Short to Ground
52=Backup Power SupplyVoltage Boost Fault
53=Primary Crash Sensor Circuits Resistance to Ground or Air Bag Diagnostic Fault
Since you had the center radio bezel off to replace the radio, I'd also check the upper center connector; maybe you bent a pin on its bulb when you reconnected it. Check the bulb's continuity with an ohm meter.
https://www.f150forum.com/f4/air-bag-...s-42-a-155660/
12=Low Battery Voltage
13=Air Bag Circuit Shorted to Ground
14=Primary Crash Sensor Circuit Shorted to Ground
21=Safing Sensor Not Mounted to Vehicle Properly
22=Safing Sensor Output Shorted to Battery Voltage
23=Safing Sensor Circuit Input Feed/Return Circuit Open
24=Safing Sensor Output Feed/Return Circuit Open
32=Driver Side Air Bag Circuit High Resistance or Open
33=Passenger Side Air Bag Circuit High Resistance or Open
34=Driver Side Air Bag Circuit Low Resistance or Shorted
35=Passenger Side Air Bag Circuit Low Resistance or Shorted
41=RH Primary Crash Sensor Feed/Return Circuit Open
42=LH Primary Crash Sensor Feed/Return Circuit Open
44=RH Primary Crash Sensor Not Mounted to Vehicle Properly
45=LH Primary Crash Sensor Not Mounted to Vehicle Properly
51=Air Bag Diagnostic Monitor Internal Thermal FuseFuse Blown Due to Intermittent Short to Ground
52=Backup Power SupplyVoltage Boost Fault
53=Primary Crash Sensor Circuits Resistance to Ground or Air Bag Diagnostic Fault
Last edited by Mod (Ret.); 03-30-2015 at 10:40 AM.
03-30-2015, 01:11 PM
#3
Member
Thread Starter
Thanks, I saw that video yesterday on my Google hunt, but wanted confirmation before throwing money at it. I have the switch/light assembly on order, so we'll see replacing it fixes it. It doesn't seem like you can just replace the bulb, and the way it's wired up I can't do a continuity check on it.
04-01-2015, 09:00 PM
#4
Member
Thread Starter
Changing out the air bag switch fixed the code 18. It's part number 4L3Z10A936AAA for the entire assembly.
I did take the old dead one apart to look at the bulb. It looks to be a simple soldering job to replace the bulb, just need to find the correct size one that'll take 12v. For whatever reason Ford used an incandescent bulb instead of an LED.
I did take the old dead one apart to look at the bulb. It looks to be a simple soldering job to replace the bulb, just need to find the correct size one that'll take 12v. For whatever reason Ford used an incandescent bulb instead of an LED.
04-02-2015, 05:43 AM
#5
Moderator (Ret.)
Changing out the air bag switch fixed the code 18. It's part number 4L3Z10A936AAA for the entire assembly.
I did take the old dead one apart to look at the bulb. It looks to be a simple soldering job to replace the bulb, just need to find the correct size one that'll take 12v. For whatever reason Ford used an incandescent bulb instead of an LED.
I did take the old dead one apart to look at the bulb. It looks to be a simple soldering job to replace the bulb, just need to find the correct size one that'll take 12v. For whatever reason Ford used an incandescent bulb instead of an LED.