TP Sensor Learned Value

On a new powertrain control module (PCM), the throttle position (TP) learned value is determined by the TP sensor value that is recognized when the ignition is first turned ON. The value is then retained in memory. This value is used as a baseline for a correlation between the TP input and the volume of intake air flow at idle. After many operating hours, deposits collect on the throttle plate and the bore of the throttle body. These deposits cause a restriction in the air flow at idle and can reduce engine performance at idle. In order to maintain engine idle quality, the PCM commands the throttle plate open slightly, correcting for the decreased air flow. Whenever this occurs, a new relationship is created between the TP sensor input and the actual throttle plate position. This relationship is the TP learned value.

When the throttle body is replaced, or the carbon deposits are removed, the TP learned value must be reset. If the value is not reset, the engine operates using stored values that are incorrect, resulting in a poor idle or hard starting. Resetting the TP learned value is required for the following conditions:

• The throttle body assembly is replaced
• The throttle valve is cleaned-Deposits can build up in the throttle body requiring periodic cleaning of the throttle valve and throttle bore area. Refer to Throttle Body Service .
• The PCM has been programmed.
• The PCM memory has been lost-as could happen with a long term power loss.

The TP learned value can be reset using the scan tool. Refer to Scan Tool Output Controls .