Two separate analog voltage signals (VTA1 and VTA2) that move in opposite directions - VTA1 increases while VTA2 decreases as throttle opens, providing redundancy and rationality checking
Known-Good Waveform
At closed throttle (idle), VTA1 should read approximately 0.6-0.9V while VTA2 reads approximately 4.1-4.5V. As throttle opens to wide open throttle, VTA1 increases to 3.8-4.7V while VTA2 decreases to 0.8-1.2V - the two signals move inversely with their sum always between 4.5-5.5V. Signals should be smooth with no steps, jumps, or dead spots throughout the entire throttle range.
Common Failure Patterns
One signal voltage stuck or not changing smoothly, sum of VTA1 and VTA2 outside 4.5-5.5V range
Cause: Failed TPS sensor circuit within throttle body assembly (carbon track wear on sensor element), requires throttle body replacement
This electronic throttle control system (ETCS-i) requires throttle body initialization procedure after battery disconnect or throttle body replacement - use TechStream or drive cycle to relearn. Monitor both VTA1 and VTA2 simultaneously and verify their inverse relationship; the ECM uses this redundancy to detect sensor failures and will set failsafe mode if correlation is out of range.
Related Diagnostic Trouble Codes
P0120P0121P0122P0123P0124
Always confirm waveform data with your vehicle's OEM service manual before diagnosing.