Intermittent “FISHBITE” type misfire or chuggle in the 1994-1995 GM 6.5

This refers to the occasional, isolated miss that occurs at medium to heavy throttle in the GM 6.5.

Most commonly, this is caused by a failure of the “Electronic Filter Harness”. The failure of this harness can set DTC’s 17 & 18. This harness is about 8” long with a male connector at one end with a female connector at the other. Located in the mid section of this harness is a molded rubber section, which contains the resistors.

The filter harness plugs into the rear of the optic sensor on top of the fuel injection pump (top rear). It connects between the optic sensor and the main engine harness under the intake manifold.

It can be changed out without removing the intake manifold, using a screwdriver to release the connector latch. With the latch released, push the connector toward the rear of the engine to disconnect. Then pull the connector and harness up out of the valley below the intake manifold so that you can reach the connector at the opposite end of the harness. This connector too has a latch that must be released before the connector can be disconnected.

Simply reverse the procedure to install the new, updated GM Electronic Filter Harness (Part #HDP1404). The filter harness can be checked for resistance, however we do not take chances with them. We replace the harness anytime we find one that is original.

If you have questions about these comments or about any of these products or any other Heath Diesel product, please feel free to contact us. Toll Free Phone 1 877 894 6266 or email sales@heathdiesel.com

- Bill Heath

Related Links:
GM Electronic Filter Harness for 1994-1997 6.5 (Part #HDP1404)
GM 6.5 Diesel Parts