Attention: TDR Forum Junkies 
Wiredawg
TDR MEMBER
I've learned a lot about the accelerator pedal position sensor (APPS) since yesterday when I had my big problem w/ it. Pulling my 5er back from a 400 mile run, I was in a small town starting up from a traffic light. All of a sudden there was a shudder and no accelerator pedal response. Thank goodness the mighty Cummins will move 27K lbs at idle, I got her out of the way and then I shut her down. The incident set a code, the useless P1693 code. I restarted the truck 3 times before I got throttle response back. Made it back to Del Rio and the same thing happened a stop light. I shut her down and restarted 3 times before I got throttle response again. I got home, unloaded the trailer and headed for Advance Auto Parts where they read the companion code P0121, which is low APPS voltage. The FSM doesn't have much except how to replace the APPS.
I called Dodge and the cost for an APPS is $380. Ouch! I searched the TDR forums but didn't find a lot of useful info.
I remembered I had a Cummins ISB electronics trouble shooting manual and sure enough they have complete APPS trouble shooting procedures. This is a good start IMHO before starting some of the other procedures I found. I tested the unit following the Cummins procedures, found loose plating on connector pin 5 of the six pin connector (not sure this was the problem), all of the resistances checked out and were w/in range.
Remove the neg battery cables. I found it was easier to test the APPS by removing the bracket bolts and turning it over to access connector pins. Remove the plastic cover from the throttle assembly (held on by two plastic anchors and screws). Remove the three 12mm bolts holding the APPS/throttle bracket. Remove the APPS connector from the bottom of the APPS/throttle bracket.
NOTE: All of these tests are key switch in off position.
Test 1. Check for open or short condition between pins on the connector. Connect ohm meter (set on 1K range) on pins 4 and 5 and read resistance pedal up and depressed. Should read 2000 to 3000 ohms. If measurement outside these parameters, replace.
Test 2. Check resistance between sensor pins. Measure w/ pedal released and depressed. Measure between pins 3 and 5. Released should read 1500 to 3000 ohms. Depressed should read 200 to 1500 ohms. Note: Released resistance should be at least 1000 ohms more than depressed. Replace unit if it dodoesn'teet these criteria.
Test 3. Check for a short to gnd in the sensor +5 VDC supply. Measure resistance between pin 5 and the engine block ground. Should read more than 100K ohms. Replace unit if less. Note: In order to accurately perform this, you need to run a jumper from the engine ground to the APPS bracket, since it is removed from the engine.
Test 4. Check for short circuit to ground in the signal wire. Measure resistance from pin 3 on the sensor side of the accelerator position sensor to engine block ground. Note: In order to accurately perform this, you need to run a jumper from the engine ground to the APPS bracket, since it is removed from the engine.
Reconnect the neg battery cables, turn the key switch to run, but don't start. Slowly depress then slowly release accelerator cable to calibrate the ECM to the APPS.
Once these tests are successfully completed, you have verified the specs of the APPS. Other test require removing the connector to the ECM and checking for shorts, grounds and opens in the wiring from the ECM to the connector feeding the APPS.
Now, I'm not 100 percent sure I won't have any more problems, but I'm fairly confident the tests showed my APPS is good and I believe I had voltage loss due to flaking plating on the APPS connector pins.
I'll let you know if I have any further problems. Hope these procedures help.
I called Dodge and the cost for an APPS is $380. Ouch! I searched the TDR forums but didn't find a lot of useful info.
I remembered I had a Cummins ISB electronics trouble shooting manual and sure enough they have complete APPS trouble shooting procedures. This is a good start IMHO before starting some of the other procedures I found. I tested the unit following the Cummins procedures, found loose plating on connector pin 5 of the six pin connector (not sure this was the problem), all of the resistances checked out and were w/in range.
Remove the neg battery cables. I found it was easier to test the APPS by removing the bracket bolts and turning it over to access connector pins. Remove the plastic cover from the throttle assembly (held on by two plastic anchors and screws). Remove the three 12mm bolts holding the APPS/throttle bracket. Remove the APPS connector from the bottom of the APPS/throttle bracket.
NOTE: All of these tests are key switch in off position.
Test 1. Check for open or short condition between pins on the connector. Connect ohm meter (set on 1K range) on pins 4 and 5 and read resistance pedal up and depressed. Should read 2000 to 3000 ohms. If measurement outside these parameters, replace.
Test 2. Check resistance between sensor pins. Measure w/ pedal released and depressed. Measure between pins 3 and 5. Released should read 1500 to 3000 ohms. Depressed should read 200 to 1500 ohms. Note: Released resistance should be at least 1000 ohms more than depressed. Replace unit if it dodoesn'teet these criteria.
Test 3. Check for a short to gnd in the sensor +5 VDC supply. Measure resistance between pin 5 and the engine block ground. Should read more than 100K ohms. Replace unit if less. Note: In order to accurately perform this, you need to run a jumper from the engine ground to the APPS bracket, since it is removed from the engine.
Test 4. Check for short circuit to ground in the signal wire. Measure resistance from pin 3 on the sensor side of the accelerator position sensor to engine block ground. Note: In order to accurately perform this, you need to run a jumper from the engine ground to the APPS bracket, since it is removed from the engine.
Reconnect the neg battery cables, turn the key switch to run, but don't start. Slowly depress then slowly release accelerator cable to calibrate the ECM to the APPS.
Once these tests are successfully completed, you have verified the specs of the APPS. Other test require removing the connector to the ECM and checking for shorts, grounds and opens in the wiring from the ECM to the connector feeding the APPS.
Now, I'm not 100 percent sure I won't have any more problems, but I'm fairly confident the tests showed my APPS is good and I believe I had voltage loss due to flaking plating on the APPS connector pins.
I'll let you know if I have any further problems. Hope these procedures help.
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