How to Test the ESC Module on a 93 Chevy Truck: An Ultimate Expert Guide

Nowadays, the engine’s main computer, the engine control module, is directly responsible for ignition control. The ignition module is that which fires the spark plugs to get your engine running. These advances in ignition technology have significantly contributed to the reliability of vehicles and the cleaner and fuel-efficient vehicles we enjoy. 

It is therefore important to test the ESC module to ensure that it is in good working order. The ESC module, also the ignition module can be tested using several tools. These include a dedicated ignition module tester, a spark tester, and a spark light. It is advisable that you get a professional to carry out the testing. 

This article explains more about the ESC module, its role, the symptoms of a bad ESC module, how to test it, and much more. 

What Is the Esc Module on the 93 Chevy Truck?

Most modern vehicles come equipped with several electronic sensors and modules that are tasked with controlling various engine functions so that the vehicle can run smoothly. Among these components is the electronic spark control module, ESC, which is also referred to as the ignition module.

This module works alongside the computer in timing the engine’s ignition system. This way, it ensures efficiency and guarantees superb performance. Another role that is specific to the ESC module is gauging the operating conditions and hence advancing or retard the timing of the ignition system. 

Under heavy load, this module will advance the timing of the ignition system to increase the power. On the other hand, the system is retarded at low throttle and cruising speeds to maximize efficiency. The ESC module performs these tasks so smoothly and automatically that it often goes unnoticed by the driver. 

How to Test Esc Module on 93 Chevy Truck

how to test esc module on 93 chevy truck

In some cases, the ESC module is housed inside the distributor and sometimes it may be a standalone unit. Either way, it is easily accessible and thus easily replaceable on some vehicles.

You may have diagnosed a faulty ESC module, but before you spend time and money on replacing it, ensure that a thorough diagnosis is performed and the module is tested by a professional. 

Testing the ESC module is best done by a professional. They tend to use special tools such as a spark tester, a dedicated ignition module tester, and a test light. The intermittent ignition failures may take longer to diagnose. 

What Are the Symptoms of a Bad or Failing Electronic Spark Control?

Since the ESC plays an important role in the operation of the engine, any signs or symptoms of it failing should be addressed immediately. Often, a failing ESC module translates to poor performance and driveability of your vehicle. Often, there will be some symptoms that will alert the driver to this issue and prompt servicing. 

Engine Performance Issues

Experiencing engine performance issues is usually the first tell-tale sign of a faulty ESC module. These performance issues may include hesitation, misfires, loss of power, and reduced fuel economy.

Engine Stalling

If your ESC module is problematic, your engine is likely to stall and you may not be able to start it again. Sometimes if you are lucky enough, you will be able to restart the engine after a short period. This is usually when the module has had time to cool off. 

Car Not Starting

A no-start or no-spark condition can also be attributed to a faulty electronic spark control module. This module works to directly control the engine spark, hence, if faulty, it leaves the vehicle without a spark. 


The ESC module, also known as the knock sensor module works to send 8 to 10 volts to the ECM to indicate there is no detonation. This module is located on the low side of the engine block.

The Trouble code 42 is an indication of a malfunction in the electronic spark timing, EST, system. Usually, during cranking, the timing is controlled by the ignition module while the ECM monitors engine speed. If the engine speed exceeds 400rpm, the ECM will send a signal to bypass the ignition module and thus switch the timing to the ECM control. An open in the EST circuit stalls the engine and sends a code 42. 

Bypassing the ESC module can be done by locating the tan wire with a black stripe under the dash on the passenger’s side. It is usually taped to the harness. Then, you can go ahead to unplug the inline connector. This disables the ESC for setting the timing. 

Final Thoughts

The ESC module is a vital component that is installed on most modern ignition systems, without which these vehicles will not run properly. If at any point you suspect that the ESC module in your vehicle has some issues, it is important to have it inspected, repaired, and tested by a professional technician.

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