The APS is a very important sensor which controls the fuel amount by transmitting the driver's accelerating intention to ECM. And it is divided into APS 1,2 because its reliability is important. The APS 1,2 are composed with the independent power and ground. APS 2 shows the 1/2 output of the APS1 and decides the fault if the ratio of APS 1,2 is different. When the APS 1 is out of order, the signal of APS 2 can be substituted instead of APS 1 and vise versa.
Checking output signals from APS 2 under detecting condition, if output signals are above the threshold, ECM sets P2128.
Item
Detecting Condition
Possible Cause
DTC Strategy
Signal check, low
Poor Connection
Short to battery in Signal Circuit
Open in Ground Circuit
Faulty APS
Faulty ECM
Enable Conditions
Ignition "ON"
Threshold Value
APS2 > 2.5V
Diagnostic Time
0.14 sec
MIL ON Condition
5 sec
Fig.1) Normal waveform of APS1 & APS2 with acceleration
Signal waveform of APS 1 & 2 shows that APS 2 increases voltage just half of APS 1 voltage increase when accelerating.