C8 2,0 HDI - BSM error A9B8: "Power Latch Relay, electrical short

This is the Forum for all your Citroen Technical Questions, Problems or Advice.

Moderator: RichardW

FrankHH
Posts: 7
Joined: 28 Dec 2023, 21:20
x 2

C8 2,0 HDI - BSM error A9B8: "Power Latch Relay, electrical short

Post by FrankHH »

I have had this 2007 Citroen C8 2,0 HDI, 100 kW (134 HP) for more than 16 year. Besides some issues, aircon faulty, and the servo motor need replacement, it has served me well, and I'm very happy with it.
Recently it wouldn't start. I had it towed to a repair shop where they started it right away and drove it indoors for fault finding. A BSI log printout said code A9B8, Power Latch Relay, electrical short to plus, local (my translation to English).
Ignition coils were checked ok, new diesel filter and new battery were installed. The car was fine.
I drove home, and the next day, the car wouldn't start, again.
I really dont like electrical faults, certainly not intermittent ones. And a BSI / BSM box code, what the heck that is anyway, sounds unpleasantly expensive.

Anyone on this forum: suggestions much appreciated, what the trouble could be, way forward, etc.
User avatar
moizeau
Donor 2024
Posts: 1608
Joined: 12 Jan 2015, 17:08
x 319

Re: C8 2,0 HDI - BSM error A9B8: "Power Latch Relay, electrical short

Post by moizeau »

When you say it doesn't start, could you give more details? Are the dash lights coming on? Does the engine turn over on the key? Etc. etc. The more info, the more chance of getting advice in the right direction.
Pete
Notice the BX is still top the list but sadly gone
FrankHH
Posts: 7
Joined: 28 Dec 2023, 21:20
x 2

Re: C8 2,0 HDI - BSM error A9B8: "Power Latch Relay, electrical short

Post by FrankHH »

Thanks for your reply.
Yes, everything appears normal, dash lights, when I turn the key the electric engine starter runs, etc. But no ignition.
Well, when the electric engine starter runs for like 10-15 seconds, there could very briefly be a sound that could indicate that ignition momentarily took place, but the engine wont run. I run the starter for perhaps 1-2 minutes, then stop, I dont want to drain the (new) battery. Rather save it for a new try the next day.
My post was imprecise, should have said "no ignition", not wont start.
The BSM error A9B8 was logged perhaps 20 km driving before I parked it, and the next day the engine would not start/ignite.
When the shop asked me, I remembered that the car very shortly, perhaps for half a sec, lost ignition on the road, then went normal again, so briefly that I hardly paid to attention to it. But that appears to be when the A9B8 error was logged.
There was no error code (and no fault) when the car was at the shop. It started right away.
User avatar
moizeau
Donor 2024
Posts: 1608
Joined: 12 Jan 2015, 17:08
x 319

Re: C8 2,0 HDI - BSM error A9B8: "Power Latch Relay, electrical short

Post by moizeau »

The code the garage gave you, to my knowledge, isn't a PSA code. A proper PSA diagnostic will give you a better idea. For a hunch, and I don't like hunches, I'd say crank sensor. Get it read properly would be my advice
Pete
Notice the BX is still top the list but sadly gone
FrankHH
Posts: 7
Joined: 28 Dec 2023, 21:20
x 2

Re: C8 2,0 HDI - BSM error A9B8: "Power Latch Relay, electrical short

Post by FrankHH »

It's the repair shop of an established Citroen dealership. Not a small garage.
I would expect it to be a proper PSA diagnostic.
User avatar
Rp0thejester
Donor 2024
Posts: 2472
Joined: 11 May 2022, 19:54
x 824

Re: C8 2,0 HDI - BSM error A9B8: "Power Latch Relay, electrical short

Post by Rp0thejester »

Are you having this issue in cold weather? Is it sporadic? sometimes starts first time sometimes doesn't? When turning the key is it just a ticking noise that can be heard or are there other noises? Oh btw, Welcome fellow C8 owner. Having read your symptoms over and over again, have you tried hitting the starter motor with a broom or metal pole really HARD whilst someone is turning the key?
Ryan

'99 Xsara 1.6 X (Red) with Sunkissed bonnet. T59 SBX
'54 Astra Estate 1.7DTI (Artic White)
'06 C8 2.2Hdi Exclusive (Aster Grey)

Champion of Where's CitroJim :-({|=
Yes I ask the stupid questions, because normally it is that simple.
FrankHH
Posts: 7
Joined: 28 Dec 2023, 21:20
x 2

Re: C8 2,0 HDI - BSM error A9B8: "Power Latch Relay, electrical short

Post by FrankHH »

Thanks for your reply Ryan
Yes. It was cold when the problem appeared. Minus 2 deg C.
Perhaps plus 4 at the garage when it started right away. Fult had dissppared
Now its plus five and problem resurfaced.
Yes sporadic, internittent.
No strange sounds that I've noticed.
Curious about your suggestion to hit stater with metal object. Why would this help? I would expect that an el short would already have connected to ground
User avatar
Rp0thejester
Donor 2024
Posts: 2472
Joined: 11 May 2022, 19:54
x 824

Re: C8 2,0 HDI - BSM error A9B8: "Power Latch Relay, electrical short

Post by Rp0thejester »

If temperature was a problem then I'd say plugs, but as it starts as and when it wants to then I'd say it's the starter motor. Get someone to turn the key whilst you hit it really hard with a long pole, you can't reach it with a hammer. If the engine tries to start after your constantly hitting the starter motor then that's the issue. Let me know if it works
Ryan

'99 Xsara 1.6 X (Red) with Sunkissed bonnet. T59 SBX
'54 Astra Estate 1.7DTI (Artic White)
'06 C8 2.2Hdi Exclusive (Aster Grey)

Champion of Where's CitroJim :-({|=
Yes I ask the stupid questions, because normally it is that simple.
User avatar
Rp0thejester
Donor 2024
Posts: 2472
Joined: 11 May 2022, 19:54
x 824

Re: C8 2,0 HDI - BSM error A9B8: "Power Latch Relay, electrical short

Post by Rp0thejester »

If the starter motor isn't kicking in as it should then you'll get no ignition. The starter motor may be seized or dead, hitting it will help to bring it back to life for a second.
Ryan

'99 Xsara 1.6 X (Red) with Sunkissed bonnet. T59 SBX
'54 Astra Estate 1.7DTI (Artic White)
'06 C8 2.2Hdi Exclusive (Aster Grey)

Champion of Where's CitroJim :-({|=
Yes I ask the stupid questions, because normally it is that simple.
FrankHH
Posts: 7
Joined: 28 Dec 2023, 21:20
x 2

Re: C8 2,0 HDI - BSM error A9B8: "Power Latch Relay, electrical short

Post by FrankHH »

The starter motor runs fine and cranks the engine, it was replaced a couple of years ago, the old one simply died.
The repair shop tested the plugs, I think they measured the amperes, no signs of trouble.
I thought it was the fuel supply and asked for the diesel filter to be replaced. Did not help. And manually pumping fuel forward, didn't help either.
So I believe it's a fault in the electric system, but the repair shop suggested to wait, maybe low voltage from old battery could disturb electronics (I had new battery installed) before they began replacing (expensive) parts. In particular as they had trouble identifying the culprit, the car was working fine at the shop, no errors.
I have no clue what the power latch is doing.
I neither have facilities or skills to fix it myself and need to have it towed to the repair shop again.
The car is now 16+ years old, fault in electrical/computer system. Could anyone tell me if it's a minor or major issue? Please cheer me up, I really like the car.
Any suggestions what I could ask the shop to look at?
/Frank
User avatar
moizeau
Donor 2024
Posts: 1608
Joined: 12 Jan 2015, 17:08
x 319

Re: C8 2,0 HDI - BSM error A9B8: "Power Latch Relay, electrical short

Post by moizeau »

If they are a proper garage they should be able to see if the crank/cam sensors are synced?
Pete
Notice the BX is still top the list but sadly gone
FrankHH
Posts: 7
Joined: 28 Dec 2023, 21:20
x 2

Re: C8 2,0 HDI - BSM error A9B8: "Power Latch Relay, electrical short

Post by FrankHH »

Issue solved.
The garage identified a minor crack in the flexible fuel hoses to the injection system. Makes some sense I guess, synthetic material becomes stiff/brittle over time and the issue started in below zero deg C.
I was told a the system is under a light vacuum, a small crack there can draw in air, starves injectors of fuel.
I'm at pains to understand how this can generate a diagnostic "Power Latch Relay, electrical short" error.
Cost of hoses sent from France, close to EUR 200 (25% VAT included) + garage labour.
Car has run flawlessly for a week now, even in cold weather, snow, nuisance weather.
Much relieved owner of an old C8 would like to thank Rp0thejester and certainly moizeau for your kind suggestions.
/Frank
User avatar
Rp0thejester
Donor 2024
Posts: 2472
Joined: 11 May 2022, 19:54
x 824

Re: C8 2,0 HDI - BSM error A9B8: "Power Latch Relay, electrical short

Post by Rp0thejester »

I'm glad you have sorted this issue and THANK YOU for letting us know the result!!! It's VERY rare that FCF gets a reply once an issue is resolved, so thanks, this will help countless people.
Ryan

'99 Xsara 1.6 X (Red) with Sunkissed bonnet. T59 SBX
'54 Astra Estate 1.7DTI (Artic White)
'06 C8 2.2Hdi Exclusive (Aster Grey)

Champion of Where's CitroJim :-({|=
Yes I ask the stupid questions, because normally it is that simple.
FrankHH
Posts: 7
Joined: 28 Dec 2023, 21:20
x 2

Re: C8 2,0 HDI - BSM error A9B8: "Power Latch Relay, electrical short

Post by FrankHH »

Another observation. Before this no-start issue appeared, the car had begun to smell. In fact, I considered pouring an expensive bottle of extra-strong exhaust system cleaner in the tank upon next diesel filling to clear out any coke/dirt in the catalyst.
I then noticed that fumes were released under the car, it was downright smoking, somewhere under the driver's seat, for 30-60 secs after having turned the ignition off.
I believe it's the turbo that runs a cleaning/cool-down cycle, correct me if I'm wrong.
Observation: After replacing the flexible fuel hoses to the injection system, those fumes have disappeared.
/Frank