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Kia Cerato P0638 Throttle Actuator Issue: Hesitation on Acceleration & Start Method Dependency

Model: Kia Cerato Fault Code: P0638 Posted: 2016-03-13 20:49

My Kia Cerato engine light is on and displays fault code P0638, indicating a throttle actuator problem. The car hesitates during acceleration under normal starting conditions. When I start the vehicle by inserting the key to position '0' and then turning it through positions I (ACC), II (ON), and III (START) without holding at 'ON', the engine starts but still hesitates when accelerating — the engine light remains on. However, if I perform a normal start with a brief hold at position II (ON) before advancing to III (START), the car starts and runs smoothly with no hesitation. The only difference is that in this case, the engine light stays on. I've reviewed repair procedures, but given cost concerns, I'm hesitant to follow every step blindly. Given that the throttle actuator appears functional under certain conditions, could the issue be related to power supply or voltage? I'm not an expert, but I'm learning — any insights would be appreciated. Thanks for your help.

Related fault codes
P0638
Comments (4)
Anonymous 2016-03-14 07:16

YEAR MAKE MODEL ENG TRANS COLOR\n'Key at 0 then turn I, II, III' — is this a sequence with timing? Specifically, are there specific time intervals or holds between the positions?

Anonymous 2016-04-17 20:26

Kia Cerato - Engine light on with P0638 code\nThe car hesitates during acceleration when started normally (key turned from I to II to III with a hold at position II). However, if the key is turned directly from I to II to III without holding at 'ON', the engine starts and accelerates smoothly. The engine light remains on in both cases.\nThis suggests the issue may not be a complete throttle actuator failure — it might relate to ignition sequence or power delivery. Is this normal behavior? Could a faulty electrical connection or voltage drop be causing intermittent throttle response? Any experienced input would be helpful.

Anonymous 2016-04-17 20:41

No, I didn't mean a time count — my explanation was unclear. Normally, when turning the ignition key: position I is 'ACC' (accessories), II is 'ON', and III is 'START'. Typically, we hold at 'ON' before moving to 'START' to allow systems to initialize. In my case, if I skip that pause and turn directly from I → II → III without delay, the car starts smoothly and accelerates normally. This indicates the throttle system may be working but sensitive to ignition sequence.\nVehicle: Kia Cerato 1.6, 2013 model (engine and transmission details may update later).

Anonymous 2021-03-11 14:57

Have you found a resolution for this issue? I have the same symptoms in my Kia Cerato with P0638 code — hesitation on acceleration, and different starting behaviors. Any solutions or diagnostics that work?