P0621 - Generator Lamp "L" Control Circuit Malfunction

**danielk** · 1st March 2011, 17:13

P0621 - Generator Lamp "L" Control Circuit Malfunction

Hi,

I've got this error code in my Signum 1.9 CDTI 120 for last 3 months. I can clear it but it come back ;(

There is a yellow spanner on the dash board for first 3-4 minutes of the day (and less than a 1 mile) and then it gone for at least 6h. I can start the car as many times I want and it won't show up again until next day ... or if car is parked for more than 6 hours.

I have found some posts about faulty or new alternator but in my car nothing has changed and the battery is charged as it should - car starts ever single time without any problems.

Can any one help? This is very annoying to see this spanner every day in the morning

**Tony12** · 1st March 2011, 17:38

Could be a glow plug if its only showing up when its cold

**Hirobofly** · 1st March 2011, 21:05

The P0621 comes from the alternator, so that is probably about to fail.....
Had the same code on mine when it had failed.

The spanner-symbol can come of a number of issues.....
Other causes might be:
- bad glowplug(s) (as Tony12 said)
- Bad injector (3rd injector-issue)
- Low Remaining Oil quality (if DPF is installed)
- Intermittent low charge/battery voltage (your P0621 will cause this to happen)

**danielk** · 5th March 2011, 13:57

thanks, will try to the change glow plugs

**SlowCoach** · 25th March 2012, 10:45

I got this issue too, altnerator is new and 100% tested working as should, 14.2 running volts so know its working and battery spot on,

Injectiors all tested spot on so won't be that

Glow plugs- starts straight away so no issues there

Could this be related to lights?? As it says "lamp" ??? My rear left fog don't come up, been cleaning etc think that area need replacement, could this be the issue?

**lee gsi** · 25th March 2012, 16:48

Nearside fog wont come on as its not wired/set to come on.

**VeCeZ22YH** · 20th June 2012, 20:57

hi.
generator was reconditioned today and put back into car. i clear the fault :
P0621 - Generator Lamp "L" Control Circuit Malfunction
(04) - Present
via op com but after next ignition the batery sing appeared on board again.
the same fault saved to DTC.
charging is good in voltage range.
could anybody help me?
thanks and please feel free with my english.
greet from Slovakia