codes P0638 and B3938, any guesses on possible faults?

[Marju]

Hi!
My Saab 9-3 (2008) needs some repairs...but what is actually wrong?

Very loud noise from motor compartment and a lot of heat when opening the hood...also, the engine went into limp mode ...

Code P0638 - throttle mechanical, can not reach closed position (throttle position deviation from demanded)

Code B3938 - solenoid fuel lid, short circuit

I am just ordinary woman, not a car mechanic (but lately had to deal with car problems).

My Saab is very very sad and unhappy, cause it wants to drive! Please help.

[Zbycholud45]

It sounds like your Saab is definitely trying to tell you something with those error codes and symptoms. Here’s a breakdown of what might be happening based on the codes and the issues you described:
1. Code P0638 - Throttle mechanical issue:

• This code means that there is a problem with the throttle body, specifically that it can’t reach the closed position correctly. The throttle body controls the amount of air entering the engine, and if it’s not working properly, it could explain both the loud noise and the engine going into limp mode.
• Possible causes:
  
  • The throttle body itself might be dirty or malfunctioning.
  • The throttle actuator (which controls the movement of the throttle) might be faulty.
  • Wiring issues or connectors between the throttle body and the engine control unit (ECU) could be causing incorrect signals.
  
  
• What to do:
  
  • Start by cleaning the throttle body—sometimes dirt or carbon buildup can cause the issue.
  • If cleaning doesn’t help, the throttle body might need to be replaced, or the issue could lie in the actuator or wiring. A mechanic will be able to diagnose this with more precision.

2. Code B3938 - Solenoid fuel lid short circuit:

• This code is related to the solenoid that controls your fuel lid. It’s a much smaller issue compared to the throttle body, but the short circuit could prevent your fuel lid from opening properly.
• What to do:
  
  • This issue isn’t urgent, but it might require replacing the solenoid or fixing the wiring that controls it. You might need a mechanic to handle this, but at least it’s not related to the engine performance!

3. Excessive heat in the engine compartment:

• The extra heat could be a symptom of the throttle body issue, especially if the engine isn’t getting enough air, causing it to run hotter than usual.
• It could also indicate a separate issue like a cooling system problem (e.g., low coolant, radiator issue, or cooling fan not working).
• What to do:
  
  • Check the coolant levels to make sure they’re adequate. If the heat issue persists, it’s worth having a mechanic inspect the cooling system to make sure everything is functioning correctly.

Limp Mode:

• Your car going into limp mode is a safety feature. It limits engine power to prevent further damage. Once the throttle body issue is fixed, this should go away.

Final Thoughts:

I understand dealing with car problems can be frustrating, especially when you're not a mechanic, but it sounds like your Saab is mostly dealing with the throttle body issue (P0638). I’d recommend taking it to a mechanic for a proper diagnosis, but in the meantime, cleaning the throttle body might help. You might also want to check the coolant levels to ensure your engine isn’t overheating.
Hope this helps get your Saab back on the road soon! ��