Component Location
General Description
Driver’s intension to accelerate is transmitted to ECM through Accelerator Pedal Sensor(APS) . And APS, whose mechanism is same as TPS, is required for ECM to determine optimum fuel injection quantity.
As fidelity of APS is strongly required, APS is devided into two. One is APS1, which outputs main signals and the other is APS2, which monitors APS1 performance.
APS1 and 2 do not share power supply and ground. Normally, APS2 output voltage is the half of APS1 and if the ratio of two signal is out of specified value, error is recognized then, Limp Home mode is activated.
When Limp Home mode is activated, engine speed is fixed at 1200RPM and driving performance is limited to prevent excessive power generation due to APS false signal.
DTC Description
P2138 is set when APS 2 output voltage which is not 1/2 of APS 1 output voltage is detected for more than 0.24 sec. Careful inspection of poor connection between APS 1 and APS 2, resistance characteristic of APS component is needed.
DTC Detecting Condition
Item | Detecting Condition | Possible Cause |
DTC Strategy | ? Voltage monitoring | ? APS 1 Circuit ? APS 2 Circuit ? APS component |
Enable Conditions | ? IG KEY "ON"with pressing accllerator pedal |
Threshold Value | ? When APS 1,2 is depressed approx. 0 ~ 5%, the difference between APS1 and 2 is above 347mV ? When APS 1,2 is depressed above 7%, the difference between APS 1 and 2 is above 405mV |
Diagnostic Time | ? 0.24 sec. |
Fail Safe | Fuel Cut | NO | ? Limp home rpm is 1200rpm. |
EGR Off | NO |
Fuel Limit | YES |
Check Lamp | YES |
Specification
| Pedal released | Pedal depressed | Sensor Type |
APS 1 | 0.7V~0.8V | 3.8V~4.4V | Variable resistance type(Potentiometer) |
APS 2 | 0.275V~0.475V | 1.75V~2.35V |
Schematic Diagram
Signal Waveform
APS 2 Ground checking signal is for ECM to monitor APS 2. This signal drops APS 2 output voltage to below 200.39mV per 200msec. If APS 2 output voltage does not drop to below 200.39mV, ECM sets DTC as recognizing ground circuit error of APS 2 .
? The waveform below 200.39mV is not detectable in Ground checking signal waveform of APS 2 signal. Instead, the waveform which drops a little is detected. If APS 2 data of "SERVICE DATA" on the Scantool varies from 350mV to 0mV periodically, it means it works well.