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Discussion Starter · #1 ·
Hi my 2006 saab 93 was playing up it went in to limp mode so i got a new refurbished ecu the saab place said he couldnt get the data off my old one so i had to take the car to them , picked car up got half way home the engine light come back on so drove it home as it drove normal tried it again it had loss of power but dont think it was in limp mode this time i checked it with my cheap scan tool it comes up knock sensor 1 circuit bank 1 or single , i rang the place where i got ecu from he told me to send ecu back which i did i fitted second one yesterday 20 min engine light came back on checked with my code reader it says the same thing knock sensor 1 circuit bank 1 or single. any suggestions where to look thank you someone said ecu isnt programmed properly, then i read could be CDM what ever that is. thank you
 

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Limp mode does not mean you have to replace the CPU. Limp mode is a high order protection/safety mode. For instance, if the accelerator position malfunctions, on start up and you put it in Drive the vehicle could thrust forward when you weren't expecting. Also, if your engine is reaching overheating range, the CPU will go into limp mode to protect the engine and possibly get you back home. A Knock sensor code should NOT put you into limp mode, knock is to control ignition timing, when it detects detonation from engine it will retard the Ignition timing to protect, but should not put you in limp mode. Check the wiring connection to the Knock sensor and the resistance as well. You can confirm operation of Knock sensor while monitoring Ignition advance data PID with OBD II code reader, tap the engine block with small hammer simulating engine Knock, the timing value should get retarded on the Knock sensor data pid.


Hi my 2006 saab 93 was playing up it went in to limp mode so i got a new refurbished ecu the saab place said he couldnt get the data off my old one so i had to take the car to them , picked car up got half way home the engine light come back on so drove it home as it drove normal tried it again it had loss of power but dont think it was in limp mode this time i checked it with my cheap scan tool it comes up knock sensor 1 circuit bank 1 or single , i rang the place where i got ecu from he told me to send ecu back which i did i fitted second one yesterday 20 min engine light came back on checked with my code reader it says the same thing knock sensor 1 circuit bank 1 or single. any suggestions where to look thank you someone said ecu isnt programmed properly, then i read could be CDM what ever that is. thank you
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Ok, the “knock sensor” is in the ignition coils. So first place to look is the ignition coils. Likely to previous owner replaced them with non oem coils, big mistake. Smaller chance that it is simply old plugs. Replace spark plugs and coils in that order and tell your shop they owe you for the ECU you prob did not need.
 

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Hi my 2006 saab 93 was playing up it went in to limp mode so i got a new refurbished ecu the saab place said he couldnt get the data off my old one so i had to take the car to them , picked car up got half way home the engine light come back on so drove it home as it drove normal tried it again it had loss of power but dont think it was in limp mode this time i checked it with my cheap scan tool it comes up knock sensor 1 circuit bank 1 or single , i rang the place where i got ecu from he told me to send ecu back which i did i fitted second one yesterday 20 min engine light came back on checked with my code reader it says the same thing knock sensor 1 circuit bank 1 or single. any suggestions where to look thank you someone said ecu isnt programmed properly, then i read could be CDM what ever that is. thank you
This link will help you
 

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Discussion Starter · #6 ·
Limp mode does not mean you have to replace the CPU. Limp mode is a high order protection/safety mode. For instance, if the accelerator position malfunctions, on start up and you put it in Drive the vehicle could thrust forward when you weren't expecting. Also, if your engine is reaching overheating range, the CPU will go into limp mode to protect the engine and possibly get you back home. A Knock sensor code should NOT put you into limp mode, knock is to control ignition timing, when it detects detonation from engine it will retard the Ignition timing to protect, but should not put you in limp mode. Check the wiring connection to the Knock sensor and the resistance as well. You can confirm operation of Knock sensor while monitoring Ignition advance data PID with OBD II code reader, tap the engine block with small hammer simulating engine Knock, the timing value should get retarded on the Knock sensor data pid.
Thank you
 
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