Airbag Code
- Thread starter mpsjr
- Start date
Frankie X
Registered
Could you at least give us a hint as to what kind of car you're asking about?
hmm... this post is in the Mark VIII section...maybe...
Oops! Mark VIII RCMs have no code 31 in their diagnostic protocol.
21 means a possible open circuit to ground for the Driver's Safing Sensor.
41 relates to open circuits to the Right Primary Crash Sensor
-no 31.
32, maybe? Open circuit to Driver's Airbag, possible Clockspring defect...
Perhaps you're miscounting, or you might be talking about some other model of vehicle.
Remember, "the LOD helps those who help themselves!"
hmm... this post is in the Mark VIII section...maybe...
Oops! Mark VIII RCMs have no code 31 in their diagnostic protocol.
21 means a possible open circuit to ground for the Driver's Safing Sensor.
41 relates to open circuits to the Right Primary Crash Sensor
-no 31.
32, maybe? Open circuit to Driver's Airbag, possible Clockspring defect...
Perhaps you're miscounting, or you might be talking about some other model of vehicle.
Remember, "the LOD helps those who help themselves!"
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More information
More information
I noticed that today, on the way home, it was flashing a 51 code. I shut off the engine when I got home, and turned the key to the "on" position. At this point, I expected to see the 51 code flashing; however, it was flashing 31 instead. I wasn't sure if it was because the car was off or not, so I cranked it up, and it continued showing the 31 code. That explains my confusion earlier, although I have no clue as to why it's changing the code.
I've checked all of the fuses/relays/etc. that I can find and they're all ok. I even checked the plugs under the seats to make sure there were positive connections all around.
Finally, I tried using a Snap-on computer to read/clear the codes, but it was unable to communicate with my car to check the airbag. I was able to check for other codes, such as the transmission/engine/etc; however, I cannot get the computer to read the airbag codes. I'm pretty much at a loss here as to what the problem is.
Anyway, thanks for your help. I appreciate it.
Matt
More information
I noticed that today, on the way home, it was flashing a 51 code. I shut off the engine when I got home, and turned the key to the "on" position. At this point, I expected to see the 51 code flashing; however, it was flashing 31 instead. I wasn't sure if it was because the car was off or not, so I cranked it up, and it continued showing the 31 code. That explains my confusion earlier, although I have no clue as to why it's changing the code.
I've checked all of the fuses/relays/etc. that I can find and they're all ok. I even checked the plugs under the seats to make sure there were positive connections all around.
Finally, I tried using a Snap-on computer to read/clear the codes, but it was unable to communicate with my car to check the airbag. I was able to check for other codes, such as the transmission/engine/etc; however, I cannot get the computer to read the airbag codes. I'm pretty much at a loss here as to what the problem is.
Anyway, thanks for your help. I appreciate it.
Matt
Roadboss
On Work Release
It won't. If you see a DTC 13 or DTC 14 this is telling you that there is a short in the system, most likely the crash sensors up on the fenders, this is likely where you are getting intermittent ground faults, because once grounded the monitor will flash DTC 51.
The other question would be has the car ever been in anaccident where the air bag deployed, and/or body panels where then crash sensors are been replaced.
The other question would be has the car ever been in anaccident where the air bag deployed, and/or body panels where then crash sensors are been replaced.
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Frankie X
Registered
OK, Matt, now we're getting somewhere.
First, Lincoln did a very bass-ackwards thing with the Mark VIII; while all of Ford's other model lines switched over to OBDII Networked Restraint Systems (some as early as 1995), the Mark VIII kept a stand-alone, "count-the-flashes" RCM right up to the end of its production.
That's why you got no codes with the OBDII scan tool.
-Code 51, "Thermal Limiter Blown"
This is not a conventional "short blows fuse" scenario.
The RCM has detected a shorted wire that could trigger one or both of the airbags to deploy at the wrong time. If this happens while the driver is just cruising down the road, minding his own business, Whoa! Accident! Injury! Death!
To prevent this, the RCM takes a cyanide pill and kills itself by overloading an internal circuit and burning out its deployment power fuse.
The RCM (which is in the middle of the dash, behind the radio) must now be replaced, but only after the underlying problem is solved.
Where's the short?
Your RCM is telling you with the alternate code you see. You've reversed the digits; it's not making a 31, it's making a 13.
-Code 13, "Deployment Circuit Short to Ground"
I'll copy'n'paste Ford's explanation.
------------
"DTC 13—Air Bag Circuit Shorted to Ground
NOTE: DTC 13 will flash only while the short to ground is present.
The air bag diagnostic monitor measures the voltage at Pin C276-11, Circuit 614 (GY/O) and Pin C276-12, Circuit 623 (P/W) of the air bag diagnostic monitor connector. The voltage at these pins varies with charging system voltage. If the air bag diagnostic monitor measures a voltage of 2.0 volts or less at Pins C276-11, Circuit 614 (GY/O) and C276-12, Circuit 623 (P/W), the air bag diagnostic monitor will flash DTC 13 to indicate a possible short to ground on these circuits; refer to Possible Causes for additional circuits that may be shorted to ground. When flashing DTC 13, the air bag diagnostic monitor opens its internal thermal fuse. This disables the air bag deployment circuit. If the voltage at Pins C276-11 and C276-12 returns to normal, a DTC 51 will be present due to the open thermal fuse; refer to DTC 51 in this section.
Possible Causes:
-Low voltage at air bag diagnostic monitor Pins C276-11 and C276-12.
-An internal short to ground within the air bag sliding contact, causing the driver side air bag circuit(s) to be shorted to ground.
-An internal short to ground within the LH kick panel safing rear air bag sensor and bracket, causing Circuit 614 (GY/O) or 623 (P/W) to be shorted to ground.
-An internal short to case ground within the driver side or passenger side air bag assembly."
------------
Roadboss has already pointed out the single most common reason for 13/51: the vehicle has been in an accident, the airbags went off, and the RCM was not replaced.
The Code 51 Diagnostic in Ford's manuals begins like this:
------------
"DTC 51 After Air Bag Deployment:
NOTE: Air bag diagnostic monitors can withstand several air bag deployments and do not need to be replaced after every deployment. Only replace the air bag diagnostic monitor if it is damaged.
Occasionally, after an air bag deploys, the internal wiring of the air bag(s) may become shorted to the metal housings of the air bag(s). This internal air bag short is detected by the air bag diagnostic monitor as short to ground in the air bag deployment wiring. Since the air bag diagnostic monitor is still operating immediately after most deployments, the air bag diagnostic monitor will detect the shorted wiring and will flash DTC 13 or 14 and open the internal thermal fuse. After the deployment, as the air bag(s) cool off, the internal shorted wiring may correct itself. The short to ground will no longer exist and the air bag diagnostic monitor will flash DTC 51. If a vehicle with a deployed air bag is flashing DTC 51, inspect and replace all the damaged areas of the vehicle that have crushed wiring, sensors, etc. If no damage is found, assume that the deployed air bag was the cause for the intermittent short and replace the air bag diagnostic monitor when the new air bag module(s) are installed.
After a short to ground has been corrected, the air bag diagnostic monitor will flash out DTC 51. DTC 51 indicates that the thermal fuse inside the air bag diagnostic monitor is open and the short to ground no longer exists.
If a short to ground has not been located and serviced (short to ground corrected itself), consult OASIS for potential wiring shorts.
If a short to ground has been correctly located and serviced, replace the air bag diagnostic monitor.
*** DO NOT replace the air bag diagnostic monitor until the short to ground has been positively located and serviced. Replacing the air bag diagnostic monitor before servicing a short to ground will result in repeat service.***"
------------
Other than that, look for an internal short within the clockspring in the steering column (I see that fairly often) or corrosion/water damage at the safing sensor behind the driver's kickpanel down low at carpet level.
If you like, follow the wires referred to in the Code 13 diagnostic. They only go to both airbags and the safing sensor.
If you're using an ohmmeter to check resistance to ground, NEVER NEVER NEVER NEVER probe the actual wires going into the airbags!!! Always unplug them when measuring deployment circuits. The power sources in most DVOMs are enough to detonate the 'bags!
Let us know what you find.
First, Lincoln did a very bass-ackwards thing with the Mark VIII; while all of Ford's other model lines switched over to OBDII Networked Restraint Systems (some as early as 1995), the Mark VIII kept a stand-alone, "count-the-flashes" RCM right up to the end of its production.
That's why you got no codes with the OBDII scan tool.
-Code 51, "Thermal Limiter Blown"
This is not a conventional "short blows fuse" scenario.
The RCM has detected a shorted wire that could trigger one or both of the airbags to deploy at the wrong time. If this happens while the driver is just cruising down the road, minding his own business, Whoa! Accident! Injury! Death!
To prevent this, the RCM takes a cyanide pill and kills itself by overloading an internal circuit and burning out its deployment power fuse.
The RCM (which is in the middle of the dash, behind the radio) must now be replaced, but only after the underlying problem is solved.
Where's the short?
Your RCM is telling you with the alternate code you see. You've reversed the digits; it's not making a 31, it's making a 13.
-Code 13, "Deployment Circuit Short to Ground"
I'll copy'n'paste Ford's explanation.
------------
"DTC 13—Air Bag Circuit Shorted to Ground
NOTE: DTC 13 will flash only while the short to ground is present.
The air bag diagnostic monitor measures the voltage at Pin C276-11, Circuit 614 (GY/O) and Pin C276-12, Circuit 623 (P/W) of the air bag diagnostic monitor connector. The voltage at these pins varies with charging system voltage. If the air bag diagnostic monitor measures a voltage of 2.0 volts or less at Pins C276-11, Circuit 614 (GY/O) and C276-12, Circuit 623 (P/W), the air bag diagnostic monitor will flash DTC 13 to indicate a possible short to ground on these circuits; refer to Possible Causes for additional circuits that may be shorted to ground. When flashing DTC 13, the air bag diagnostic monitor opens its internal thermal fuse. This disables the air bag deployment circuit. If the voltage at Pins C276-11 and C276-12 returns to normal, a DTC 51 will be present due to the open thermal fuse; refer to DTC 51 in this section.
Possible Causes:
-Low voltage at air bag diagnostic monitor Pins C276-11 and C276-12.
-An internal short to ground within the air bag sliding contact, causing the driver side air bag circuit(s) to be shorted to ground.
-An internal short to ground within the LH kick panel safing rear air bag sensor and bracket, causing Circuit 614 (GY/O) or 623 (P/W) to be shorted to ground.
-An internal short to case ground within the driver side or passenger side air bag assembly."
------------
Roadboss has already pointed out the single most common reason for 13/51: the vehicle has been in an accident, the airbags went off, and the RCM was not replaced.
The Code 51 Diagnostic in Ford's manuals begins like this:
------------
"DTC 51 After Air Bag Deployment:
NOTE: Air bag diagnostic monitors can withstand several air bag deployments and do not need to be replaced after every deployment. Only replace the air bag diagnostic monitor if it is damaged.
Occasionally, after an air bag deploys, the internal wiring of the air bag(s) may become shorted to the metal housings of the air bag(s). This internal air bag short is detected by the air bag diagnostic monitor as short to ground in the air bag deployment wiring. Since the air bag diagnostic monitor is still operating immediately after most deployments, the air bag diagnostic monitor will detect the shorted wiring and will flash DTC 13 or 14 and open the internal thermal fuse. After the deployment, as the air bag(s) cool off, the internal shorted wiring may correct itself. The short to ground will no longer exist and the air bag diagnostic monitor will flash DTC 51. If a vehicle with a deployed air bag is flashing DTC 51, inspect and replace all the damaged areas of the vehicle that have crushed wiring, sensors, etc. If no damage is found, assume that the deployed air bag was the cause for the intermittent short and replace the air bag diagnostic monitor when the new air bag module(s) are installed.
After a short to ground has been corrected, the air bag diagnostic monitor will flash out DTC 51. DTC 51 indicates that the thermal fuse inside the air bag diagnostic monitor is open and the short to ground no longer exists.
If a short to ground has not been located and serviced (short to ground corrected itself), consult OASIS for potential wiring shorts.
If a short to ground has been correctly located and serviced, replace the air bag diagnostic monitor.
*** DO NOT replace the air bag diagnostic monitor until the short to ground has been positively located and serviced. Replacing the air bag diagnostic monitor before servicing a short to ground will result in repeat service.***"
------------
Other than that, look for an internal short within the clockspring in the steering column (I see that fairly often) or corrosion/water damage at the safing sensor behind the driver's kickpanel down low at carpet level.
If you like, follow the wires referred to in the Code 13 diagnostic. They only go to both airbags and the safing sensor.
If you're using an ohmmeter to check resistance to ground, NEVER NEVER NEVER NEVER probe the actual wires going into the airbags!!! Always unplug them when measuring deployment circuits. The power sources in most DVOMs are enough to detonate the 'bags!
Let us know what you find.
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Thanks for your help. I've got the car scheduled to go in next week. Before I bought it, my Mark had been driven through some "high water" that was apparently high enough to come over the door seal. The previous owners drove a little too fast and water got into the intake, locking up the engine. I was able to find a motor with 12,000 miles on it for pretty cheap. That and new carpet were the only things that I had to replace until now. Your comment about the corrosion/water damage could be spot on, but I don't have the time to get into electrical problems myself.
At any rate, I appreciate your insight, although I doubt this is something that I can fix on my own. I might be decent with motors and mechanics, but electronics are lost on me. I'll let you know what turns up to be the problem
Again, thanks.
At any rate, I appreciate your insight, although I doubt this is something that I can fix on my own. I might be decent with motors and mechanics, but electronics are lost on me. I'll let you know what turns up to be the problem
Again, thanks.
Today the shop called and said that the airbag computer is blown and it has to be replaced before anything further can be diagnosed. According to Frankie's post, if the computer (monitor) is changed without finding the short, then it's just going to happen again.
Fortunately, if the shop replaces the part and it goes out again, it should be covered under warranty. We'll see what happens.
Fortunately, if the shop replaces the part and it goes out again, it should be covered under warranty. We'll see what happens.
Roadboss
On Work Release
I would be sure that they know that you have info about this, and are going to have them liable to find the short, if there is one and not to come back to you if it blows because of a short. I just call that being heads up with one another, just in case they have a tech who doesn't understand what FrankieX explained to you. Wonder if this happens again in a week or month? Just my thought. Good luck and I hope they get it right for you.
Frankie X
Registered
They might be right.
I have seen the short actually be inside the RCM within the airbag output driver circuits to one of the airbags. It's not very common, but it's also not unheard of.
In my experience, maybe one in twenty of the cases where first generation restraint systems generate 51 and 13 or 14 can be repaired with only an RCM replacement.
They've given you their diagnosis and made a commitment to you. If it turns out they're wrong and an external short they missed takes out the new RCM, that's their problem, not yours.
I have seen the short actually be inside the RCM within the airbag output driver circuits to one of the airbags. It's not very common, but it's also not unheard of.
In my experience, maybe one in twenty of the cases where first generation restraint systems generate 51 and 13 or 14 can be repaired with only an RCM replacement.
They've given you their diagnosis and made a commitment to you. If it turns out they're wrong and an external short they missed takes out the new RCM, that's their problem, not yours.
Roadboss
On Work Release
Frankie-I just wanted him to make sure,because you know there are some techs out there who don't, and some would then try and blame another condition. I just wanted him to be able to make a claim against the warranted work even if they did a half ass job on the diagnosis.
Well, I got the car back today. I was told it was the airbag controller. The total job cost $550, but at least the light isn't flashing anymore.
The mechanic that worked on my car is very qualified. I gave him the information from Frankie and he took a look at it, did a diagnosis, and came to the conclusion that the controller was the problem. He also assured me that if the light comes back on, he'll find the problem and fix it. Hopefully the problem won't return, but we'll keep our fingers crossed.
Thanks again to everyone for all of your insight into this matter. I appreciate everything.
Matt
The mechanic that worked on my car is very qualified. I gave him the information from Frankie and he took a look at it, did a diagnosis, and came to the conclusion that the controller was the problem. He also assured me that if the light comes back on, he'll find the problem and fix it. Hopefully the problem won't return, but we'll keep our fingers crossed.
Thanks again to everyone for all of your insight into this matter. I appreciate everything.
Matt
Roadboss
On Work Release
"I gave him the information from Frankie and he took a look at it, did a diagnosis, and came to the conclusion that the controller was the problem. He also assured me that if the light comes back on, he'll find the problem and fix it. Hopefully the problem won't return, but we'll keep our fingers crossed."
That's what I felt would afford you the best possible protection from getting into a p_ssing contest with the dealer. Nice to see the Christians win one once in a while.
That's what I felt would afford you the best possible protection from getting into a p_ssing contest with the dealer. Nice to see the Christians win one once in a while.