Engine Knock Control Sensor Issue

petrolHead1 · May 18, 2016

Dear all, I am having a 2007 Toyota Belta which I purchased one year back. Recently a slight jerk was noticed when slowing down from around 50 to lower speeds. The jerk happens only once during the slowdown and occurs very rarely. Therefore, I went to reputed mechanic and he did a OBD scan. Even though the check engine light was not lit up, an error code was recorded which indicated that the engine knock control sensor was malfunctioning. Have any of you guys experienced this problem?? If so, please shed some light regarding this matter. :( Thanks in advanced.

FYI I bought it when the ODO meter reading was 67 000 and now its 84 000 kms. A full tune up and a CVT gear oil change was done when purchased.

Rumesh88 · May 19, 2016

According to the observations given it is highly unlikely that you have a problem with the knock sensor or even if it has some issue it may not be related to the jerk you are experiencing. Instead could you get a mechanic to test your Throttle Position Sensor (TPS) for any dead spots along its range of motion. TPS is nothing but a variable resistor and should show a steady variation of resistance as the throttle goes from closed to wide open. Please keep in mind that an engine miss of this nature can be due to one of many possibilities. BTW what's the engine type (2NZ)?

hrm · May 19, 2016

I think the engine should be either 1KR (1000cc) or 2SZ (1300cc). Can you hear knocking sound by any chance?

petrolHead1 · May 19, 2016

On 5/19/2016 at 3:21 AM, Rumesh88 said:
According to the observations given it is highly unlikely that you have a problem with the knock sensor or even if it has some issue it may not be related to the jerk you are experiencing. Instead could you get a mechanic to test your Throttle Position Sensor (TPS) for any dead spots along its range of motion. TPS is nothing but a variable resistor and should show a steady variation of resistance as the throttle goes from closed to wide open. Please keep in mind that an engine miss of this nature can be due to one of many possibilities. BTW what's the engine type (2NZ)?

I will check the TPS and let you know. The engine is 2-SZ (1300cc). :)

petrolHead1 · May 19, 2016

On 5/19/2016 at 3:56 AM, hrm said:
I think the engine should be either 1KR (1000cc) or 2SZ (1300cc). Can you hear knocking sound by any chance?

No knocking sound was noticed. :)

Rohnd · May 20, 2016

On 5/19/2016 at 4:58 PM, petrolHead1 said:
No knocking sound was noticed. :)

Even at high speed on acceleration and at load (say more than 50 Km/h and climbing a small hill) you don't hear knocking/pinging sound?.

If Yes, this could be the most common symptom of malfunctioning the Knock Sensor.

With respect to others ideas, you must check TPS , cleanliness of the Throttle Body and engine oil deposits etc

PerfMad · May 20, 2016

Just curios are these knock sensors are in M/T cars as well ? IF so what exactly does this knock sensor do?

Rumesh88 · May 20, 2016

On 5/20/2016 at 5:37 AM, PerfMad said:
Just curios are these knock sensors are in M/T cars as well ? IF so what exactly does this knock sensor do?

Knock sensor detects ignition detonation and makes corrections to ignition timing accordingly. In almost all EFI engines ignition timing is based on a look up table stored in the ECU which is kept updated on the fly based on input from the knock sensor. In OP's case he seems to be referring (IMO of course) to a slight jerk but not the kind of severe jerk and the sound you get in case of a detonation.

PerfMad · May 20, 2016

On 5/20/2016 at 8:05 AM, Rumesh88 said:
Knock sensor detects ignition detonation and makes corrections to ignition timing accordingly. In almost all EFI engines ignition timing is based on a look up table stored in the ECU which is kept updated on the fly based on input from the knock sensor. In OP's case he seems to be referring (IMO of course) to a slight jerk but not the kind of severe jerk and the sound you get in case of a detonation.

Is the something that can be controlled while we engage the first gear with little lesser gas ? the knock we get can be minimized with this sensor too ? just wanna get an idea

Rumesh88 · May 20, 2016

On 5/20/2016 at 8:16 AM, PerfMad said:
Is the something that can be controlled while we engage the first gear with little lesser gas ? the knock we get can be minimized with this sensor too ? just wanna get an idea

Ignition timing is something we cannot control but (particularly in pre-1990 cars with mechanical timing control) when you get a continuous knocking sound you can stop it by backing off the throttle a bit. The knocking that we discuss here is different from the jerk you feel when you have an engine miss. I hope I understood your question correctly.