Wiring Harness & PCM Programming Services

for the

GM Generation III+ Engines

jeep_conversion_wiring_harnessOne of the most significant things an installer can do to speed the conversion process along and keep the headaches at bay is to have their factory GM harness simplified and modified. Novak has gotten this wiring process and PCM programming down to a science.

Wiring Harness

Typically, the conversion installer will get the factory engine harness from the donor vehicle. This will include every wire and connector between the PCM and the engine's sensors (Oxygen, Throttle Position, Crank Position, etc.) and the active systems (coil triggers, injectors, IAC, etc.).

Novak can simplify this harness, removing unnecessary circuits, consolidating circuits, rerouting and labelling for a simpler 5-6 wire hookup into any Jeep.

Vehicle Speed Sensor

This sensor will allow you to run a conventional cable drive speedometer and send critical speed data to your GM PCM for proper powertrain operation.

Harness Mods at a Glance :

  • Install DLC port for installation in the Jeep cab
  • Provide fuel pump relay and simplified fuel pump circuit
  • Provide a simplified and water-tight power distribution center with standard ATC style fuses and relays
  • Simplify main 12V and main Ground circuits
  • Front & rear O2 sensors will be retained. Rear O2 sensors may be programmed out if requested by customer and permitted by your jurisdiction
  • Provide an easy-to-install MIL lamp
  • Provide VSS leads
  • Fully inspect all circuits
  • Install a standalone air conditioning control circuit
  • Provision for standard shift or automatic shift (typ. 4L60E) transmissions
  • Minorly damaged harnesses can be repaired. For more extensive damage, reasonable additional costs will be determined
  • Five wire hookup (manual trans option) or seven wire hookup (automatic trans option)
  • Park / Neutral safety switch will be added for Jeeps that originally did not have this circuit
  • All trunks and branches are arranged and wrapped with new split-loom and made to more appropriate, standardized length for Jeep vehicles.
  • A pull-up resistor is installed on the tachometer signal wire for a stronger signal, required on many aftermarket tachometer solutions.
  • If you are wishing to keep your 1996-2006 XJ / TJ factory tachometer, consider Novak's tachometer emulator module, as seen here.

Fuse Block

Pictured left is the extra heavy duty relay used in our rebuilds for radiator fan control.

Identifying your GM PCM

GM Generation 3+ PCM's come in three major styles as follows:


The early Generation III PCM, 1997 to 1998


The late Generation III PCM, 1999 to mid-2007


The Generation IV PCM w/transmission controller, 2005-2020

Make sure your PCM and harness are compatible, if they were not pulled from the same vehicle. Intermixing PCM's and harness can yield unexpected results. Always consult us on this before moving forward.



Add A/C Request Eliminate EGR Electric Fan

Note: Wiring harness builds during some seasons may require more time than our usual quick turn-around. If time is of the essence, contact us.

Disclaimer: Any modifications to the Novak harness as provided, without the express written permission of Novak, will void the warranty. This includes any cutting of wires, modification of lengths, or changes to connectors - even if they are part of non-utilized circuits such as unused emissions, evap, or other features. If these are unused in your situation, leave them intact and tie them securely against the harness

Computer Programming at a Glance:

  • Remove Vehicle Anti-Theft (VATS) functions
  • Reprogram important speed sensitive functions for tire size and axle ratio
  • Remove requirement for rear O2 feedback (optionally, if applicable to your laws)
  • Remove E85 (Flex-Fuel) complications
  • Verify proper computer operation
  • Switch from 4L80E to 4L60E (or vice versa) if applicable
  • Any desired follow-up programming (up to three times) is included in the original price (shipping costs excluded)

Please note that if your PCM or its wires are damaged or in need of repair before it can be used, you may incur an up-charge for the additional labor.

Shipping Instructions


Need a cool way to attach your PCM to your Jeep? Our PCM mounting bracket assembly solves problems of placing and mounting your PCM in your engine bay.

Please see our Contact page, where you'll find our physical address to which you can send your harness and/or computer. When shipping, we recommend you insure your harness for the typical value of a new replacement harness, which is commonly ~$900 and computer for ~$250. We will associate your Shopping Cart order with your harness/computer when they arrive.

Please do not send anything other than the harness with your shipment. We do not need the throttle pedal, fuse box, battery terminals, or any other sub harnesses, just the engine wiring harness. If you are not sure if it is part of the engine or GM chassis harness, send it and we'll discard as necessary.

Make sure to let us know your phone number and e-mail address when ordering. The Novak shopping cart will ask for these details. We are likely to call or e-mail you with any questions and confirmations.

Please contact our sales staff for accurate lead times. Also, please allow shipping time as you've chosen (Ground, Third Day, Second Day, etc.)

Wiring Harnesses in Conversions

Also See