To all the jumpstarter....do it the user manuals way 
Airbag ECU after doing jumpstart not correctly
Airbag ECU after doing jumpstart not correctly
SRS Airbag ECU controll unit *inside pic* of blown one
- Thread starter austrian type-R
- Start date
I assume the SRS light came on after the improper jump start? Were is the ECU located, and is it easy to get to and remove? Are you going to try to repair it or replace it? The reason I'm asking is because the SRS light has been on since I purchased the car and I haven't taken the time to trouble shoot it. I was thinking maybe the clock spring needed to be replaced, but maybe the previous owner didn't follow the proper jumping procedure and I need to start my investigation with the ECU.
The SRS ECU is a bitch to get at. It's in the center console approx under the shifter. You have to peel back the carpet on both sides in order to get at the 4 screws that hold it in. They were installed with some kind of lock-tite and are very difficult to remove. Some have suggested using heat from something like a soldering iron to make them easier to unscrew. There are two connections on the side facing the rear. First step in diagnosing is to look for the SRS fuse in the block on the left side of driver's footwell. If its blown, replace it. If it blows again, it gets complicated as basically you need to get a test cable from the dealership in order to measure voltages on a bunch of pins and then there's a multi-page flowchart in the repair manual to figure out what's wrong.
Good luck.
Good luck.
So, I am curious, how do you do an incorrect jumpstart?
Incorrect: Battery to Battery. Correct Battery to the NSX fuse box like in the user-manual. Check your fuse at the driver side feet area, left. It has a yellow plastic over the fuse. If it is okay, the SRS unit should be okay, if it is blown, you may need a new SRS unit.
Now I am really curious!
The jump start terminal in the main fuse box (engine compartment ) is solidly connected to the + terminal on the battery. Aside from the incredible hassle of trying to attach a booster cable directly to the battery + terminal, it is not apparent why connecting to the battery terminals would result in damage. I can certainly understand that if they reversed the polarity during the jump start process, things would go badly.
The jump start terminal in the main fuse box (engine compartment ) is solidly connected to the + terminal on the battery. Aside from the incredible hassle of trying to attach a booster cable directly to the battery + terminal, it is not apparent why connecting to the battery terminals would result in damage. I can certainly understand that if they reversed the polarity during the jump start process, things would go badly.
Yeah I know, but sometimes things are wired. Also most people do not have the spare wheel installed, so it is easy acess to the batterie. I can tell you a customer of mine burned the radio and the SRS unit after a jump start at the batterie. Sure, you can alwáys think that this would have happen on the terminal too, but also most the EPS ECUs are burned doing a jump start at the batterie.
As an electrical engineer, I agree with Old Guy and I'm having a difficult time believing that jumping at the battery would cause failures in the SRS unit or the radio. In fact, the picture of the ruptured capacitor seems more consistent with the leaking capacitor problem that I've personally seen in the the BOSE amps, my own TCS ECU, and my own SRS ECU.
If you energize an electrolytic capacitor with the polarities reversed, the internal leakage current of the capacitor can go quite high. If there is nothing in the circuit to limit the leakage current, the high current can cause the capacitor to self destruct. Since some / a lot of/ all the NSX electronics bits seem to have a predilection for premature capacitor failure, an accidental reversal of the polarities during the jump start process could have been the nudge that caused the damage.
That said, the SRS doesn't get powered up until the ignition key is turned. Even with a mostly dead in car battery, there should have been a lot of sparking when they attempted to connect the cables if the polarities were reversed and I think it should have been obvious that something was up before they even attempted to turn the key. Perhaps they did everything right and it was just a matter of coincidence that the ageing capacitors failed at the same time.
It is also possible that on power up of the SRS, there is a brief voltage transient internal to the SRS power supply. If the capacitors are good, that transient may not be a problem. If the capacitors are ageing or are marginal, the transient may cause the capacitors to fail. That could explain a scenario if the SRS persistently fails on power up.
That said, the SRS doesn't get powered up until the ignition key is turned. Even with a mostly dead in car battery, there should have been a lot of sparking when they attempted to connect the cables if the polarities were reversed and I think it should have been obvious that something was up before they even attempted to turn the key. Perhaps they did everything right and it was just a matter of coincidence that the ageing capacitors failed at the same time.
It is also possible that on power up of the SRS, there is a brief voltage transient internal to the SRS power supply. If the capacitors are good, that transient may not be a problem. If the capacitors are ageing or are marginal, the transient may cause the capacitors to fail. That could explain a scenario if the SRS persistently fails on power up.
Thanks for the info Ian!
I understand and agree .. but in austrian type R's second post, he clarified what he meant by 'incorrect' and 'correct' and the implication was that by 'incorrect', he meant jumping directly at the battery instead of the in the engine compartment. There was no suggestion that anyone has crossed the +/- .. that would likely have caused more damage that just a few caps.
Yes, I only talk about jump starting it directly at the batterie, but you should fo it at the fixed terminal in the engine bay. Second, why people reporting toasted electronics after jump starting the car?
Yes to all!
Just trying to hypothesize an explanation for an event that, based upon the cars physical arrangement should not occur! I do not deny that the failures reported by Austrian type-R occurred. However, every other car that I have had experience with jump starts from the battery just fine without damaging the electronics and they all have similar devices to the NSX (with or without failure prone capacitors).
If Austrian type-R's customers were jump starting from the battery terminals, they must have been unaware of the infinitely more convenient jump start terminal in the engine relay panel. If they are unaware of the jump start terminal, perhaps they are unaware of the +/- thing, or forgot or whatever. Just trying to hypothesize an explanation for the series of events (and customers are not always forthcoming with the details that lead up to problems!). Or perhaps it is just coincidence that the failure prone capacitors failed during the boost process.
Just trying to hypothesize an explanation for an event that, based upon the cars physical arrangement should not occur! I do not deny that the failures reported by Austrian type-R occurred. However, every other car that I have had experience with jump starts from the battery just fine without damaging the electronics and they all have similar devices to the NSX (with or without failure prone capacitors).
If Austrian type-R's customers were jump starting from the battery terminals, they must have been unaware of the infinitely more convenient jump start terminal in the engine relay panel. If they are unaware of the jump start terminal, perhaps they are unaware of the +/- thing, or forgot or whatever. Just trying to hypothesize an explanation for the series of events (and customers are not always forthcoming with the details that lead up to problems!). Or perhaps it is just coincidence that the failure prone capacitors failed during the boost process.
I think austrian type-R was talking about the potential surge issue on jump starting the car.
It’s nothing new and this topic has been there for years and even the international/local standard test procedures are defined in ISO, JIS, JASO, etc.
Honda has its own internal company test standard that is much more strict than the above standards.
For the clarification, the damage on the SRS unit shown in the post #1 was not caused 'directly' by jump starting the car based on how far the leaked capacitor acid travelled over the circuit board and also the depth of the penetration from the surface of the board causing the changes in the board colour.
From the photo, it was easy to tell that it was like that for years.
Not clear from post #5 but sounded like he experienced blown fuse #1 that triggered the SRS warning light.
If the fuse was blown, it was the result of leaky capacitors C23 & 24 on the circuit board causing damage to the nearby transistor 2SC3694 and created short circuit.
This could be 'indirectly' triggered when the car was jump started under several conditions (connecting/disconnecting the jump lead without stopping the engine first, big difference of battery voltage, etc) when the SRS unit was already partially damaged with leaky caps and just waiting for the tiny 'trigger' to pop the nearby transistor.
Unless you replace the two caps and the transistor, the short circuit will be always there and keeps blowing the fuse #1 .
I have seen exactly the same damage on many SRS units with the leaky caps at exactly the same location (C23 & 24) blowing the fuse #1 and triggering the SRS warning light.
It's the same issue as the A/C CCU board, Bose speaker AMP, Dash gauge instrument, etc.
Some examples that I repaired only under the written agreement from the owners stating that they will take full responsibility for using such repaired item when it should have been replaced.
This was caused over many years mainly by heat and not related to jump starting the car at the battery.
Probably it's already happening on your NSX if you own the very early model.
Again, same as your CCU, Bose AMP, etc.....
Fortunately, someone on here reported that exactly the same circuit board (but in different outer case/housing) were being used on old Legend models so may be it’s safer to replace the circuit board with a used one (as long as it’s not involved in an accident) than trying to repair.
Although the subject of surge issue in the automotive industry was there for years, it only became as a popular discussion when more and more modern cars started using 10s or even more than 100 of controllers across the chassis using CAN bus, etc.
Also, the introduction of hybrid highlighted the potential danger of dealing with not only the surge but also the high power (voltage, electrical current) devices.
F1 mechanics and circuit marshals were warned on this subject when hybrid technology was first introduced on F1 cars several years ago.
It all depends on so many factors such as the voltage difference between the two batteries/cars, design spec of ACG and voltage regulator, whether the engine was running or not at the time when the jump cable was connected as well as removed, what other components were in operation on both cars (especially the aftermarket ICE, etc), etc so it’s still rare but surge can damage the on-board controllers such as ECU, power window controller, EPS, etc (I'm talking about general controllers and not specific to NSX).
Again, I must stress it's still rare cases.
However, for the road rescue people, since they have to jump start the cars without knowing any backgrounds or spec of many cars, the chances of causing controller damages increases a lot compared to ordinary owners.
In Japan, JAF (similar to AA, RAC, etc in UK, AAA in US??) already had jump starter pack equipped with clean power source but from several years ago, they started carrying the surge protection device in order to minimise the potential damages to the controller devices while jump starting the customers car.
I have never seen even a single issue of jump starting NSX using standalone spare battery or even using old cars by connecting the jump lead directly at the battery or at the jump start terminal inside the engine bay as long as you take pre-caution such as minimising the voltage difference, stopping the engine before disconnecting, etc.
The load dump is the worst condition when it comes to the surge.
When jump starting the NSX using another car (rescue car), you should follow the recommended method in the owner’s manual (not the one for the NSX but for the rescue/donor car) especially if the rescue car is from the modern era.
NSX would be fine but it could be a different story for your modern rescue car.
Kaz
It’s nothing new and this topic has been there for years and even the international/local standard test procedures are defined in ISO, JIS, JASO, etc.
Honda has its own internal company test standard that is much more strict than the above standards.
For the clarification, the damage on the SRS unit shown in the post #1 was not caused 'directly' by jump starting the car based on how far the leaked capacitor acid travelled over the circuit board and also the depth of the penetration from the surface of the board causing the changes in the board colour.
From the photo, it was easy to tell that it was like that for years.
Not clear from post #5 but sounded like he experienced blown fuse #1 that triggered the SRS warning light.
If the fuse was blown, it was the result of leaky capacitors C23 & 24 on the circuit board causing damage to the nearby transistor 2SC3694 and created short circuit.
This could be 'indirectly' triggered when the car was jump started under several conditions (connecting/disconnecting the jump lead without stopping the engine first, big difference of battery voltage, etc) when the SRS unit was already partially damaged with leaky caps and just waiting for the tiny 'trigger' to pop the nearby transistor.
Unless you replace the two caps and the transistor, the short circuit will be always there and keeps blowing the fuse #1 .
I have seen exactly the same damage on many SRS units with the leaky caps at exactly the same location (C23 & 24) blowing the fuse #1 and triggering the SRS warning light.
It's the same issue as the A/C CCU board, Bose speaker AMP, Dash gauge instrument, etc.
Some examples that I repaired only under the written agreement from the owners stating that they will take full responsibility for using such repaired item when it should have been replaced.
This was caused over many years mainly by heat and not related to jump starting the car at the battery.
Probably it's already happening on your NSX if you own the very early model.
Again, same as your CCU, Bose AMP, etc.....
Fortunately, someone on here reported that exactly the same circuit board (but in different outer case/housing) were being used on old Legend models so may be it’s safer to replace the circuit board with a used one (as long as it’s not involved in an accident) than trying to repair.
Although the subject of surge issue in the automotive industry was there for years, it only became as a popular discussion when more and more modern cars started using 10s or even more than 100 of controllers across the chassis using CAN bus, etc.
Also, the introduction of hybrid highlighted the potential danger of dealing with not only the surge but also the high power (voltage, electrical current) devices.
F1 mechanics and circuit marshals were warned on this subject when hybrid technology was first introduced on F1 cars several years ago.
It all depends on so many factors such as the voltage difference between the two batteries/cars, design spec of ACG and voltage regulator, whether the engine was running or not at the time when the jump cable was connected as well as removed, what other components were in operation on both cars (especially the aftermarket ICE, etc), etc so it’s still rare but surge can damage the on-board controllers such as ECU, power window controller, EPS, etc (I'm talking about general controllers and not specific to NSX).
Again, I must stress it's still rare cases.
However, for the road rescue people, since they have to jump start the cars without knowing any backgrounds or spec of many cars, the chances of causing controller damages increases a lot compared to ordinary owners.
In Japan, JAF (similar to AA, RAC, etc in UK, AAA in US??) already had jump starter pack equipped with clean power source but from several years ago, they started carrying the surge protection device in order to minimise the potential damages to the controller devices while jump starting the customers car.
I have never seen even a single issue of jump starting NSX using standalone spare battery or even using old cars by connecting the jump lead directly at the battery or at the jump start terminal inside the engine bay as long as you take pre-caution such as minimising the voltage difference, stopping the engine before disconnecting, etc.
The load dump is the worst condition when it comes to the surge.
When jump starting the NSX using another car (rescue car), you should follow the recommended method in the owner’s manual (not the one for the NSX but for the rescue/donor car) especially if the rescue car is from the modern era.
NSX would be fine but it could be a different story for your modern rescue car.
Kaz
wow! Thanks!
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