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 the 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, consolodating 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
  • Retain or eliminate rear (post-catalytic) O2 sensors, as requested
  • Provide an easy-to-install MIL lamp
  • Provide VSS leads
  • Fully inspect all circuits
  • Optionally, install a standalone air conditioning control circuit
  • Eliminate complicated E85 (Flex-Fuel) circuits if requested
  • 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)
  • Electric fan control circuit and relay can be added, optionally
  • Park / Neutral safety switch can 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 lengths for your particular vehicle.
  • A pull-up resistor is installed on the tachometer signal wire for a stronger signal, required on many aftermarket tachometer solutions

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-present

Wiring harness modification service, GM Gen III+ engine / transmission control
Part #:
10.0000 lb
* Yes+ $30.00
* Yes
* Yes
* Yes

Computer Programming at a Glance:

  • Remove Vehicle Anti-Theft (VATS) functions
  • Reprogram important speed sensitive functions for tire size and axle ratio
  • Remove rear O2 sensors (optionally, if applicable to your laws)
  • Remove E85 (Flex-Fuel) complications
  • Verify proper computer operation
  • Switch from 4L80E to 4L60E (or vica versa) if applicable
  • Any desired follow-up programming (up to three times) is included in the original price (shipping costs excluded)
Programming, Powertrain Control Module, GM. Remove VATS, calibrate to tire size, axle ratio, add upd
Part #:
3.5000 lb

Shipping Instructions


Need a cool way to attach your PCM to your Jeep? Our PCM mounting bracket assembly is the best thing to come along in this area for some time.

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.

Currently, typical turnaround time is under 12 days, plus shipping time as you've chosen (Ground, Third Day, Second Day, etc.)

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.

Wiring Harnesses in Conversions

Also See