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TSB 18-09-99

Common Diagnostic Trouble Codes Caused By An Open Fuse.

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Date: May 21, 1999

Models: 1999 BR/BE Ram

1999 (AB) Ram Van
1999 (AN) Dakota
1999 (BR/BE Ram Truck
1999 (DN) Durango
1999 (TJ) Wrangler
1999 (WJ) Grand Cherokee
1 999 (XJ) Cherokee

Discussion:

Recent quality analysis has revealed an issue with repeated repairs for the same Diagnostic Trouble Code (DTC). The DTC may be due to an overlooked open circuit used to power the component in question. In most instances, either the circuit fuse has been erroneously removed or the fuse itself has an open (blown).

The component in question, and its circuit, are often protected by two fuses. It is usually the lower amperage fuse that is either missing or open.

The lower amperage fuse is positioned electrically in the circuit between the component in question and either a relay (Auto Shut Down, 02 heater) or the ignition switch. The lower amperage fuse will be located either in the underhood Power Distribution Center (PDC) or in the instrument panel Junction Block.

The lower amperage fuse is often missing because it was removed erroneously for use in another low current circuit. If the lower amperage fuse is open (blown), then the circuit and component in question must be checked for an electrical short. Check to make sure that the open fuse was not exchanged with another fuse or was damaged by an installed accessory.

NOTE: IF AN OXYGEN SENSOR IS REPLACED, VERIFY THAT THE CIRCUIT FUSE IS GOOD. AN OXYGEN SENSOR HEATER, WHEN DAMAGED OR OVERHEATED, MAY SHORT THE CIRCUIT AND CAUSE THE FUSE TO OPEN (BLOW).

The higher amperage fuse should be checked, but is not normally the cause of the DTC. The higher amperage fuse is located in the underhood PDC. It is positioned electrically in the circuit between the battery and either the relay (Auto Shut Down, 02 heater) or the ignition switch.

Refer to the applicable Diagnostic Procedures Manual and/or Service Manual (Group 8) for further technical assistance.

The following is a list of the components frequently replaced Erroneously due to an open fuse. Included are the possible DTC(S) which would be generated as a result. 

  1. Oxygen Sensor (02)
  2. Leak Detection Pump (LDP)
  3. Evaporative Purge Solenoid (DCP)
  4. Torque Converter Clutch -Solenoid (TCC)

notes:

POLICY: Information Only

From Bob B. - The TSB discusses the problem when a DTC (diagnostic trouble code) from a component in the vehicle. It reviews that the component (sensor, computer, etc) may be causing the problem from an open fuse. Most components of that controlling nature are protected by 2 fuses. The lower amp fuse is in the circuit and is usually the closest to the component. Often the fuse is blown or removed for use in another location thus disabling the component. The higher amp fuse is located just after the battery and may control several lower amperage circuits. For example, if a O2 sensor is replaced for any reason, check the circuit fuse for the sensor. When the sensor is damaged or overheated the fuse may blow and open the circuit.

This seems like a lot of wasted paper to remind the techs the look for blown fuses FIRST when a DTC is noted. But, it must be a problem to provoke a TSB!!!


Thanks to Bob Bergevin for supplying this TSB information

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This page was edited on: May 3, 2004