Description

NOTE: Only perform this test when directed to do so. This drive test is only designed to resolve a Code 5 condition. Performing this test for any other reason will often lead to incorrect diagnosis of system problem and incorrect replacement of components.


PURPOSE
This drive test assumes that pinpoint test Code 5 has been completed. If this is not the case, complete the test before proceeding. System Pre Check
If the pinpoint test Code 5 is not successful in resolving the system concern, this drive test can be used to conduct additional, more in depth, diagnostics.

NOTE: This drive test is designed to induce a Code 5 if there is a symptom that can create a Code 5 on a repeatable basis. Carefully record the data when performing the drive test. It is important to know what part of the drive test you are in when diagnostic trouble Code 5 is detected.

Drive Description
Discuss with the customer to determine if the vehicle was in four wheel drive when the light came on. During normal 4x2 anti-lock operation, the anti-lock electronic control unit energizes the dump solenoid a maximum of 16 times without interruption. Conditions experienced in 4x2 operation will not require more than 16 dump pulses. If the anti-lock electronic control unit notices that conditions call for a 17th dump pulse, it assumes there is a problem with anti-lock electronic control unit, deactivates the system (turning the REAR ABS warning light on), and sets a Code 5. During normal 4x4 operation, the anti-lock electronic control unit only allows 16 dump pulses but does not deactivate the anti-lock electronic control unit or light the yellow REAR ABS warning light if more than 16 dump pulses are requested. If, for reasons described below, the anti-lock electronic control unit receives incorrect information from the 4x4 switch, and therefore improperly assumes the vehicle is in 4x2, a Code 5 will often be improperly set. The most common reasons for incorrect information being sent to the anti-lock electronic control unit are:

^ 4x4 indicator switch worn or damaged.

^ Vehicle wiring concern in Circuit 210 (LB) between the 4x4 indicator switch and the anti-lock electronic control unit.

^ Customer has switched from 4x4 to 4x2 but the transfer case has not yet disengaged.

NOTE: The customer must also enter an anti-lock stop, at the same time, for this event to occur.

^ AWD system does not properly disengage upon brake application.