Repair 7

The control module of a vehicle is basically the computer that does the thinking for an engines control system. It affects the functioning of things ranging from a vehicles charging system to its transmission. This is why when the control module goes bad, the engine suffers functionality issues as well.

Voltage Overload

One of the main things that can cause a control module on a vehicle to go bad is voltage overload. This can occur when a short exists in the circuits of either a solenoid or actuator. Replacing the control module will do no good if these shorts are not dealt with as the replacement control module will experience voltage overload as well.

Water

Another thing that can cause a vehicles control module to go bad is water. Circuits get shorted out and the control modules electrical connections are harmed from the corrosion that builds if water manages to reach the inside of the control module. This is why repairs are usually not even attempted on control modules that come out of flooded vehicles.

Vibration and Stress

Vibration as well as thermal stress has also been known to cause control modules to go bad. This is because they can cause tiny cracks to form in the control modules circuit boards. However, unlike water damage, this type of damage to a control module is repairable.

General Motors (GM) introduced the Chevrolet Trailblazer as an upscale version of the Blazer in 1999. The 2002 Trailblazer has a six-cylinder 4.2-liter engine with sequential fuel injection. This engine requires a fuel pressure regulator -- also known as the fuel control regulator -- to maintain the pressure in the fuel system at the correct level. The replacement procedure for the fuel control regulator is the same for all Trailblazers.

Instructions

1

Remove the cable from the negative battery terminal. Open the filler cap on the fuel tank to release the pressure in the fuel tank.

2

Connect a fuel pressure gauge to the pressure fitting on the inlet fuel line. Place the bleed hose of the fuel gauge into a container approved for gasoline. Open the valve on the pressure gauge to relieve the pressure in the fuel system. Drain the fuel from the pressure gauge into the container, then disconnect the pressure gauge from the pressure fitting.

3

Disconnect the outlet resonator for the air cleaner with a socket wrench. Release the retaining clips for the main wiring harness on the front of the engine, then detach the wiring harness.

4

Remove the vacuum line from the fuel control regulator. Clean the surrounding area with a shop rag. Release the retainer on the fuel return line for the fuel control regulator, then detach the fuel return line. Release the retainer for the fuel control regulator with a socket wrench. Detach the regulator from the fuel rail. Discard the O-ring on the fuel control regulator.

5

Install a new O-ring to the new fuel control regulator, and coat the O-ring with engine oil. Push the new fuel pressure regulator into its housing on the fuel rail. Attach the retainer for the fuel control regulator, and tighten it to 71 inch-pounds with a torque wrench.

6

Attach the retainer for the fuel return line to the fuel control regulator. Tighten its retainer screw to 71 inch-pounds with a socket wrench. Connect the fuel return line for the fuel control regulator.

7

Fasten the filler cap on the fuel tank, and connect the cable for the negative battery terminal with a socket wrench. Turn the ignition on for two seconds to prime the fuel system, then turn it off for 10 seconds. Turn the ignition back on and check for fuel leaks. Connect the engine wiring on the front of the engine, and attach its retaining clips. Install the resonator for the air intake.