Chrysler RAM50/D50/Arrow 1979-1993 Repair Guide

Closed Throttle Position Switch

Print

OPERATION



See Figure 1

The Closed Throttle Position switch (CTP) is located either in the TPS (3.0L and 3.5L engines) or in the Idle Speed Control Motor (ISCM) assembly (2.4L engines). The CTP sends electrical signals to the ECM, telling it whether the accelerator is depressed or released. The ECM regulates the idle-speed control motor based upon those signals. Voltage within the ECM is applied, by way of the resistance, to the CTP. When the foot is taken off of the accelerator, the CTP is switched on and the current is grounded. As a result, the CTP voltage changes from a high to a low level.

If there is an abnormal condition of the CTP output even though the results of the check of the CTP and harness, the cause may be either improper adjustment of the accelerator cable or the cruise control cable, or improper adjustment of the fixed Speed Adjusting Screw (SAS).



Click image to see an enlarged view

Fig. Fig. 1: The location of the CTPS on the 3.0L engine is inside the Idle Speed Control Motor (ISCM)

HARNESS TESTING



See Figure 2

The 1993, rear-wheel drive 2.4L (California) Pick-ups have the same engine controls as the 3.0L engines. All other 2.4L engines are listed as 2.4L engines.



Click image to see an enlarged view

Fig. Fig. 2: The CTPS harness testing procedure-2.4L engines

Unplug the harness connector going to the CTP and turn the ignition ON. Measure the power supply voltage of the CTP terminal 4. If the voltage is not 4 volts or higher, repair or replace the harness between the CTP terminal 4 and the ECM terminal 6, otherwise the harness is fine.

3.0L Engines See Figure 3

  1. Unplug the ECM harness connector and the TPS connector. Check for an open or short-circuit between the CTP terminal 2 and the ECM terminal 14 or 67. If there is an open or short-circuit, repair or replace the harness between the two terminals 2 and 14.
  2.  
  3. Plug the ECM harness connector back into the ECM. Check for continuity from the TPS terminal 1 to ground. If no continuity is found, repair the harness. TPS terminal 1 and ECM terminals 17 and 24.
  4.  
  5. Turn the ignition switch ON and measure the power supply voltage of the CTP terminal 2. If the voltage is not 4 volts or higher, replace the ECM with a new unit.
  6.  

COMPONENT TESTING



2.4L Engines

The 1993, rear-wheel drive 2.4L (California) Pick-ups have the same engine controls as the 3.0L engines. All other 2.4L engines are listed as 2.4L engines.

  1. Unplug the idle speed control motor position sensor harness connector.
  2.  
  3. Check the continuity between terminal 4 and the body ground. When the accelerator pedal is depressed, the continuity should be nonexistent (infinite resistance). When the accelerator pedal is released, resistance should be existent (0 ohms).
  4.  
  5. If the CTP is out of specifications, replace the Idle Speed Control Motor (ISCM) assembly.
  6.  

3.0L Engines

  1. With the accelerator pedal released, check that the throttle valve lever or the fixed Speed Adjusting Screw (SAS) is pushed.
  2.  

If the fixed SAS is not pushed, adjust the fixed SAS.

  1. Unplug the TPS harness connector.
  2.  
  3. Check for continuity between the TPS connector terminals 1 and 2. When the accelerator pedal is depressed, there should be no continuity (infinite resistance). When the pedal is released, resistance should be evident (0 ohms).
  4.  



Click image to see an enlarged view

Fig. Fig. 3: The CTPS harness testing procedure 3.0L engine

If there is no continuity when the accelerator pedal is released, loosen the TPS installation screw; then, after turning the TPS all the way clockwise, check again.

  1. Replace the TPS (with the built-in CTP) if there is a malfunction.
  2.  

REMOVAL & INSTALLATION



Since the CTP switches are located in other components, refer to those components for removal and installation procedures. That is, for the 2.4L engine, refer to the idle speed control motor position sensor, and for the other engines, refer to the TPS procedures.

 
label.common.footer.alt.autozoneLogo