A number of tools make diagnostics easier. They allow you to measure electrical activity on circuits and components that would otherwise be undetectable. Digital Volt-Ohmmeter (DVOM) A 10-megaohm digital volt-ohmmeter (DVOM) or multimeter, such as essential tool J-39200 (Fluke 87) or equivalent, is useful for testing different aspects of circuit operation. The Fluke 87 Digital… Read More »
The most valuable reference source is the Service Manual. For 1994, light duty trucks service manuals have been reorganized to make them easier to use. The Driveability and Emissions (Diesel) Service Manual contains all the information necessary for diagnosing fuel and emissions systems. Driveability and Emissions (Diesel) Service Manual The Driveability and Emissions manual is… Read More »
Underneath its electronics, the 6.5L EFI diesel engine is a basic V8 diesel powerplant. The fuel pump, lines, and injectors still deliver fuel according to the basic rules of hydraulics. Electronics simply make them operate more precisely. Your understanding of the 6.5L mechanical systems and how they relate to each other is still indispensable for… Read More »
DATA LINK CONNECTOR (DLC) TERMINAL “B” — DIAGNOSTIC REQUEST When grounded to terminal “A”, terminal “B” allows the MIL to flash diagnostic trouble codes. DATA LINK CONNECTOR (DLC) TERMINAL “G ” — FUEL PUMP DLC terminal “G” allows technicians to enable the fuel pump to test for proper pump operation. CKT 490 from terminal “G”… Read More »
The Data Link Connector (DLC) is installed in the vehicle so a functional check of the engine’s electronic control system can be made at the factory. The DLC also allows service technicians to use the PCM’s self-diagnostic system to check the status of various components used in the engine’s electronic control system (figure 5-59). This… Read More »
Description The transmission output speed/vehicle speed sensor is mounted on the driver’s side of the transmission case, near the rear (figure 5-56). The sensor consists of a permanent magnet surrounded by a coil of wire. It reads the rotation speed of a 40-toothed ring mounted to the rear carrier assembly on 4L80E models or to… Read More »
Non-EFI 6.5L diesels equipped with the 4L80E transaxle use a dedicated Transmission Control Module (TCM) to provide shift control timing, TCC apply and release, and line pressure control. The TCM has been eliminated on 6.5L EFI vehicles. Its duties are now performed by the PCM. PCM inputs and outputs for transmission control for the 4L60E… Read More »
The PCM uses brake switch input information to interrupt cruise control operation when the brakes are applied. On automatic transmission vehicles, there are two brake switches: a normally open cruise control brake switch and a normally closed torque converter clutch (TCC) brake switch. Both send signals to the PCM alerting it to disengage cruise control.… Read More »
CRUISE CONTROL SWITCH Description The cruise control switch assembly contains three internal discrete switches that open and close according to cruise control requests by the driver. The PCM receives inputs from these switches to control fuel delivery through the fuel driver module and solenoid. Cruise Control Switch Circuit Operation The cruise “ON/OFF,” set/coast, and resume/accel… Read More »
The PCM uses information about cruise control status, brake and clutch switch status, and vehicle and engine speed for fuel delivery (figure 5-52). Three cruise control modes are used by the PCM: ON/OFF request; resume/accelerate request; and set/coast request.