Error: 140405 Undervoltage


yesterday I tested the SC2 Pro for the first time and had to find out in the end that the engine shuts off in a harder impact.

Sometimes the software displays the error: 140405.

Software: 1.0.7
Game: iRacing

  • Engine shuts off completely
  • Steering movements in the game are no longer possible
  • In TD, the engine is no longer detected
  • It takes a while until the engine is recognized in the software and then you can again activate the High Torque mode and continue driving
  • LEDs on both power supplies are lit.

Have such problems already occurred or what else could I test?

Many thanks

No such problems have been reported, so you are the first one. Can you confirm that both power supplies are connected to Simucube? Important: Please power off Simucube, then disconnect the AC (mains) side power cords, and wait a while, and only after this verify that the power cables are connected to Simucube 2 itself.

Have again tested some things:

  • Power supplies removed and waited for 10min --> Blue lights are off

  • Pins of the power supply and motor controlled by the power supply -> i.O.

  • Power supply in the base and the tightness of the plug checked -> i.O. (with one minimally looking further even though both are locked in place)

  • Power supply units in the socket

  • Base switched on -> moves up normally

  • In the wall -> Base off

  • Plug off the power supply units in the motor reversed

  • In the wall -> Base off

  • If I set the “overall strength” to 75% (18.8NM / 17.1A), the error does not occur anymore, but as soon as I go higher, then the engine completely exits after a crash

Had the same issue with my SC2 pro for a few hours.
Pulled power supply cords out of the Base for a few seconds.
After that no problems anymore.
I assume it must have something to do with just one working power supply.

Yeah, thats what we are thinking as well.

then plug in just one power supply and try again and then the other.
Then you should identify that power supply which is causing the problem.

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Yes, it should be possible to identify if either of the units is outright failed, or if a connector on the Simucube is the culprit. Would be a first occurrence of either of these issues.

Have now tried different variant with the power supplies:

  • Power supply 1 in SC2 IN1 -> Motor starts up
  • Power supply 2 in SC2 IN1 -> Motor starts up
  • Power supply 1 in SC2 IN2 -> motor starts up
  • Power supply 2 in SC2 IN2 -> Motor starts up

For all 4 variants, the engine is recognized by the software.

But I have not tested in the game, whether the error persists with a power supply. Only if the engine is normally recognized by the software.

Was that right or should I test something else?

You should test for example maximum torque against the endstop effect at 100% strength with quick steering movements. This should match any extreme situation.

But please, you and all others reading, restrain to doing such tests only for diagnostic purposes. We do not recommend running the Simucube 2 Pro device with just one PSU for any prolonged period.

Like I said on other post, two PSUs was one of my mayorn concerns about SC2 Pro to not buy it and go for the Sport. Potential failures x2 (home failures or SC2 failures or both)

@mika reading your suggestions about diagnosis test (testing with only one PSU on the Pro), I have deduced thats NEW safety firmaware is necesary on the Pro, SC2 must know in every moment if both PSUs are running or not.
Imagine that @andre was with one faulty PSU for a long period without issues or thinking that is a HandsOffDetection feature… That would damage the SC2 base?

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That’s a great suggestion @Alfye20.

It would be a reassuring feature to have in True Drive if at all possible.

Perhaps a line of text in the main startup tab, similar to the one that tells us if the emergency stop is released or not. A couple of check boxes that are ticked, showing that each of the supplies are detected?

The hardware does not have means to measure voltages separately.

Hi @Andre, one possibility is that the two PSUs are not perfect matches for each other. I.e. if their voltage output is too much different, then one PSU would get overloaded and shut down on peaks.

Do you happen to have a multimeter which you could use to check the output voltages of PSUs while disconnected from SC2?

@Tero, yes I have a multimeter to test, but I need the pin assignment, so there is no short circuit.

@Mika, i will test this evening after work

Good! Could you measure voltages of both PSUs? Here’s how:

Just avoid any contact with skin and shorting the pins for safety. It’s ~48 VDC on the pins.


@Tero & @Mika
Have tested things:

  • Output voltage of both power supplies 48.63VDC & 48.33VDC

  • Input voltage of both power supplies remains constant at 232VAC in a crash

  • Power supply 1 in the IN1 -> at the end stop quick steering movement -> error does not occur

  • Power supply 1 in the IN2 -> at the end stop quick steering movement -> error does not occur

  • Power supply 2 in the IN1 -> at the end stop quick steering movement -> error does not occur

  • Power supply 2 in the IN2 -> at the end stop fast steering movement -> error does not occur

What I noticed is that in a crash with both power supplies, the LED’s go out and are immediately back.


It could be the case that the voltage difference between two PSUs is large enough to cause this issue.

SC2 draws power from PSU that has higher voltage, so if difference is large enough, then higher voltage PSU faults before lower voltage PSU begins supplying. It would cause chain reaction where higher voltage PSU trips first, then all load goes to lower voltage PSU and that trips too (so both PSUs will be off then).

Perhaps easiest solution here is that we’ll replace one of the PSU’s with unit that has better matching voltage. How does it sound?

I am grateful for any help I receive from you.

If the replacement of the power supply is the first guess of you, then I accept the help thankfully and we can try it out.

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Glad to hear your feedback! I’ll arrange someone from us to handle the case. Lets think overnight whether the PSU swap is the best approach, or do we get better ideas.

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If you are going to swap power supplies it would make sense for you to choose 2 at the factory.
And make sure they are closely matched and replace both to the customer?