top of page

LS Harness and ECM Info

Where and what to purchase with Discovery LS Swap Kits

It is best to purchase your engine before purchasing an LS engine harness. That way you can look at the engine and see what parts your harness needs. We always advise that you purchase a Discovery LS Kit before purchasing an engine or any other parts. While we try to keep all parts lists updated, the parts list with your kit may have deviations from the Discovery LS sample parts list.

Harness Purchasing

There are 3 main options for getting an LS harness:

  • Buy a new, custom-made harness for your LS engine (we typically recommend using PSI Conversions, BP Automotive, or Speartech). Recommended.

  • Have one of the above companies or another company rewire a GM factory harness.

  • Rewire a GM factory harness yourself (for information see Note that most LS factory harness at this point are 15-20 years old and might have damage.

Harness Options
When purchasing a harness there are several options that need to be made:

  1. The harness needs to be drive-by-cable (DBC) setup for a Vortec 24X Gen 3 engine with the red-blue plugs.

  2. The harness needs to be setup for a manual (T56) or non-electric automatic transmission.

  3. Choose the harness option for injectors based on the engine you have. There are three options (EV6, Multec, and EV1).

  4. If MAF options are given, use the 5 pin truck MAF from 99-07.

  5. For alternator, choose the 4 pin option if given, even though the Land Rover alternator is used in the conversion.

  6. If MAP options are given, use what is found on your engine, most commonly Delphi.

  7. A/C is not needed on the GM harness.

  8. Cruise control is not needed on the GM harness.

Harness Notes

  • Use online references to figure out what injectors you have. If you get a harness with the wrong injectors, injector pigtails can be used to fix the issue (often less than $20). Most 4.8 and 5.3 Vortec engines use Multec or EV6 injectors.

  • Drive-by-wire (DBW) harnesses are not currently supported, so make sure you buy a drive-by-cable (DBC) harness.

  • The cheap, new eBay harnesses are not worth the risk (usually). Many we have seen are not properly wired or have had some sort of issue. Additionally, many times the eBay harnesses need an adapter from a 3+2 pin MAF to a 5 pin MAF and injector adapters. Your mileage may vary, but using these harnesses is at your own risk.

  • If you have a harness for a different application or setup, it may be able to be converted. For example, an automatic transmission harness may be converted to a manual harness by removing the wires and pins from the ECM connector (see for an idea of what is entailed). This, however, doesn't work in all cases.

  • In addition to an LS harness, you will still need to modify your factory Land Rover Discovery harness using the instructions provided with the Discovery LS Kit. Alternatively, we can rewire your factory Land Rover harness for you.

ECM Options
There are several options for purchasing and tuning an GM ECM.

  • Buy an ECM from the company who built your harness. Recommended for ease of use.

  • Buy an ECM from a junkyard (can be found using and send it off for a mail order tune (like

  • Buy an ECM from a junkyard and buy HPTuners or EFI Live and tune the ECM yourself. Recommended for most options.

ECM Notes

  • For the easiest solution, buy the ECM from the company building your harness.

  • Our kits do not currently support any aftermarket ECMs (like Holley EFI). The only ECM currently supported by our Discovery LS Kits is the drive-by-cable 12200411 "red-blue" PCM commonly found in 2001 Silverado 1500s.

  • ECMs must be tuned to the specifications stated in the manual! Incorrect values will cause issues. Let your manufacturer or tuner know about the values needed that are stated in the manual.

  • ECMs come generally with a base tune. This is normally enough to get the engine up a running. For best fuel economy and performance, find a local tuner to tune your engine to your Discovery. Road tuning should be sufficient. 2wd chassis dyno tuning should not be used.

  • The harness-related parts (MAF, O2 sensors) stated in the Discovery LS Kit Sample Parts List are for cost estimation only. Use the parts directed by your harness manufacturer.

  • Buying the tuning software and tuning the ECM yourself can be a great way to get to know the LS engine, but is not recommended for those who want the setup to be the most straightforward. There are many tuning guides online that show you how to delete VATS and other necessary things to get up and running.

bottom of page