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Brad
Brad, Dealer Technician
Category: Transmissions
Satisfied Customers: 7751
Experience:  ASE Master,(L-1) Certified, Transmission Specialist
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1999 Dodge Durango 5.2 4x4 134000 miles, ok speedometer

Customer Question

1999 Dodge Durango 5.2 4x4 134000 miles, ok speedometer intermitantly works and not works, replaced speed sensor in transmission, transmission does not slip or constantly shift in and out of overdrive, fluid clean. After replacing the speed sensor and
driving vehicle I noticed that once in a while the speedometer will move like the tach, if I'm sitting still and rev engine speedo needle will actually move just like the tach,. Also when this happeds my abs light will come on but no codes appear. When speedo
works normal abs light goes off. Anyone ever seen this, I'm thinking maybe the cluster is bad but dont want to send it out for repair to find its a bad ground or something and waist money. Any help would be greatly apretiated.
Submitted: 1 year ago.
Category: Transmissions
Expert:  Brad replied 1 year ago.

Have you checked the RWAL sensor in the rear axle which actually is responsible for the speedometer?

Expert:  Brad replied 1 year ago.

Check the wiring to the sensor and OHM across the 2 terminals.. If OL replace it..

Expert:  Brad replied 1 year ago.

Did you get my reply?

Customer: replied 1 year ago.
Ok sorry for taking so long had to get vehicle back from my kid. Anyway have changed rear speed sensor in dif, still does the same thing but now I'm coming up with a genaric code for output speed sensor, I unplug it makes no diferance speedometer still bounces up and down even sitting still. Going to test wires and see if there is a break in it someplace. What should they ohms at?
Expert:  Brad replied 1 year ago.

Do you know what P codes are setting? Also since the RWAL sensor is new check the white and red wires to the ABS module and also disconnect the ABS module and check for any moisture.

Customer: replied 1 year ago.
Ok if I scan it under chrysler it says fault in comunication but if I scan it under obd2 world it comes up with P0720 Genaric output speed sensor circuit. I will check those wires what am I looking for at those wires voltage or ohms? Also will check plug on module. Thanks
Customer: replied 1 year ago.
Well plug dry, tested wires, lrg red/green- 12volts, red/ blue-12volts, lrg black /red -neg, white/pink-neg, dodn't get anything from any others.
Expert:  Brad replied 1 year ago.

The code you have is P-0720 LOW OUTPUT SPEED SENSOR RPM, ABOVE 15 MPH. The Output sensor is in the tailshaft of the transmission.. Here is a case on the speedometer bouncing.

Case Number999926183

Vehicle IssueSpeedometer Erratic or Above Zero when Stationary => Diagnose and Repair as Required.;What is the symptom or condition being addressed ? >> Electrical issue - miscellaneous What type of transmission or final drive concern is this ? >> Automatic transmission / transaxle - includes electrical What type of electrical issue is being addressed ? >> Speedometer operation issue What type of speedometer operation issue is being addressed ? >> Speedometer above zero with vehicle stationary >> Speedometer above zero with vehicle stationary >> Speedometer erratic - pointer jumps high / low >> Speedometer erratic - pointer jumps high / low Can you duplicate or verify the reported condition ? >> Yes - condition can be duplicated intermittantly >> Yes - condition can be duplicated intermittantly >> Yes - condition can be duplicated constantly >> Yes - condition can be duplicated constantly Did you perform a search for bulletins that may relate to the issue being addressed ? >> No - bulletin search will be done before proceeding >> No - bulletin search will be done before proceeding >> Yes - bulletin search has been done >> Yes - bulletin search has been done

System or ComponentCustomer Concern (No DTCs);Automatic Transmission / Transaxle;Yes - Intermittent,Yes - Continuously

RecommendationSee recommended diagnosis and repair directions provided. Speedometer operation is erratic or speedo is above zero with vehicle stationary. Check for excessive radio frequency interference (RFI) or short to voltage that may cause erratic vehicle speed sensor signal (VSS) or transaxle output speed sensor signal. See applicable service manual section (8) for wiring diagram. Most service manuals are available on MDS2 machine. RFI CHECK PROCEDURE: [A]: MODELS USING TRANSAXLE OUTPUT SPEED SENSOR TO OPERATE THE SPEEDOMETER: See applicable service manual section (8) / Instrument Panel or Cluster section for speedometer circuit wiring diagram. Unplug the transaxle output speed sensor connector from the wiring harness. Connect voltmeter or lab scope to the transaxle output speed sensor wiring harness connector. Increase / decrease engine RPM several times. Voltmeter or lab scope should remain at zero indicating no voltage or RFI is present. If voltage or RFI is detected see suggested repair procedure below. RS MODELS: On (RS) models examine main wiring harness routed near transaxle solenoid pack and fluid pan. The wiring harness may be chafed in this area causing shorted circuit wiring. Repair as required. : MODELS USING VSS TO OPERATE THE SPEEDOMETER: See applicable service manual section (8) / Instrument Panel section / Speedometer section for vehicle speed sensor location and circuit wiring diagram. Unplug the vehicle speed sensor connector from the wiring harness. Connect voltmeter or lab scope to the speed sensor wiring harness connector. Increase / decrease engine RPM several times. Observe the voltmeter or lab scope. Vehicle speed sensor signal should remain at zero indicating no voltage or RFI is present. If voltage or RFI is detected see the suggested repair procedure below. REPAIR FOR EXCESSIVE RFI: Excessive RFI may be produced by surrounding wiring such as spark plug wires or generator wiring. Check for vehicle speed sensor or transaxle output speed sensor circuit wiring routed too close to spark plug wires / other. Reposition circuit wiring harness as required. Suggest use zip ties or other suitable fasteners. If short to voltage is detected repair circuit wiring harness as required. IMPORTANT: Check for electrical add-on equipment that may cause the condition being addressed. Remove electrical add-on equipment if required. Suggest discuss situation with owner.

Customer: replied 1 year ago.
Ok tested wires from output speed sensor with them unplugged from sensor, both wires are recieving 2.55 volt with vehicle running. Tested them both from the plug and at the ecm still 2.55 volts. Also ohmed the wires and getting good connection so no broken wires. Could the ecm be bad and that be why I can't get any comunication with abs module. Also I unplug the abs module and the speedometer stops bouncing. Not sure where to go from here other than start buying parts.
Customer: replied 1 year ago.
Just triesd something else I turned ignition on engine not running and tested wires still getting 2.35 volts on both wires. Didn't think there was supposed to be any voltage from what I understood with the diagnostic you sent.

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