Duramax questions, answered.

That is our current lead time and we take great pride in meeting our agreed completion dates. If we are running longer the website will be adjusted to reflect accordingly. Watch the video How to Send and What to Expect for all of the details on timing.

For $576.00 your LB7, LLY, LBZ or LMM Duramax ECM/TCM (engine to chassis from a pickup truck) harness is reworked to standalone and comes back refreshed. Right now turnaround is 2 weeks.

For an additional $500.00 you can also send your upper engine harness to us for a complete refresh. It will also be completely peeled, degreased and inspected then recovered with high temp tubing and tape. This applies to standalone harness conversions only.

When your donor harness arrives it will be Tagged, Peeled, Degreased and fully Inspected under magnification. When that process is complete you will be contacted by phone (3-4 business days after arrival) to build up the work order for your specific setup. From that point the harness will be finished and ready to ship within the 2 weeks time frame.

It will arrive looking like a new harness since we only use High Temp Split Loom Tubing, GM Spec High Temp Tape, and printed plastic Labels. No butt connectors, gooey household electrical tape, swap meet loom or masking tape anywhere!

Minor repairs to crash or rodent damaged wires (up to 10) are included in the standard price. If you have damaged or missing connectors, replacements will be quoted on our work order call. We stock every connector for Duramax and Allison so your lead time won’t be longer if a replacement connector is needed.

Please remove everything that can be disconnected before shipping any harness for conversion.

ECMs, TCMs, Modules, Sensors, Brackets, Pedals and extra sections like the Duramax Accelerator Pedal Jumper or the Transfer Case Jumpers should not be sent. Battery cables should also be removed if you plan to reuse. Any extra items will be cut off and disposed. We do not retain, stock or sell replacements of any of these items. If you think you might want it pull it off and keep it on your end.

Fill in Start Send In with your name, email address, phone number and return address, and pay for your send-in online: the service plus insured return shipping in the continental U.S. Print the packing sheet you receive and put it inside the box with your harness.

Expect a work order phone call 3–4 business days after your harness arrives. You pay for your send-in online when you fill in the Start Send In form. Any extra work found at the work order call is invoiced separately.

Due to labor availability constraints and to streamline efficiency, Email is our primary means of communication. We check and respond to email multiple times daily. If you have checked the website and your question is not answered here or in one of our FAQ videos, a telephone appointment can be set up via email request.

You must detail the reason for the call in your email and we can set a time/date for a conversation. Questions that are already answered on the website will be directed back to the site.

We regret to do this but we have no choice because the Tariff costs are unsustainable: All International shipments will ONLY be accepted if shipped via the POST OFFICE (e.g., Canada Post transfers to USPS) due to Tariff collection issues on both inbound and outbound packages.

If you ship a package from another Country via any other shipping service (UPS, FedEx, DHL) it will be refused and it will go back to the distribution center. Once we have proof the tariff has been paid we will accept the package.

Just ship via your Post Office and they will handle collection of the Tariff. We will only return ship International from USPS who will transfer to your post office. They will collect the return Tariff at delivery to you. Packages sent to us within the United States are unaffected.

Please do not ship any modules to us. You need to retain your modules and work with the tuner directly.

Yes. Our All New One Piece Standalone harnesses are built new in our shop for the LBZ (2006–2007) and LMM (2007.5–2010), for pickup truck engines only. They are not for Van, Kodiak or TopKick.

Choose your options in the Shop, add the harness to your cart, and pay at checkout with PayPal, Pay Later, or a debit or credit card.

Insured FedEx Ground, 5–7 days, for a flat $58.63.

We only support standalone conversions of Duramax harnesses and nothing else. A standalone harness is intended for engine swaps in vehicles that did not originally have a Duramax Engine from the factory. Generally, the swapped vehicles are pre 1996.

We can not work on any harness going back into any GM truck newer than 1996 due to Federal Emissions Regulations.

Due to the complexity of modern vehicles and their control systems we specifically avoid any “Plug and Play” type swaps. Nothing about a standalone harness will plug into the vehicle you are working on. All tie in is completely up to the installer/customer and is not something we support in any way.

This is the same as the plug and play answer. Note: older engines in newer trucks (such as an LB7 in a truck newer than 2004) is the same answer. Federal Emission laws prevent us from providing this service.

Topkick/Kodiak’s are known for having communication problems. They have unique circuits for the GPCM, Coolant Bottle and Transmission Internal harness and we no longer support these harnesses. Email for more details.

At this time we only support Duramax and our R&D is closed for taking on projects outside of the Duramax Family.

We only support Allison Transmissions when they are part of a Duramax Swap.

Most of our customers use the Allison Transmission that was originally paired with the Duramax from the factory. If using an Allison please note that the 5 speed must be used with LB7 and LLY and the 6 speed must be used with the LBZ and LMM.

The 4L80/85E that was in a Van type Chassis is another option and others choose the ZF6 Manual that was also available from the OEM. Your choices are only limited to what will bolt up to the engine. We can set up the harness to work with just about anything including Marine Transmissions, Pulling Truck Clutch Only and Air Boat Gear Reduction Boxes.

Please email for more details on modifying the harness when swapping the transmission that was bolted to your Duramax when it left the factory.

We no longer sell individual parts, terminals or connectors to the public but will happily support our current and previous harness customers with the parts they need.

We do not offer any changes in length. Every harness leaves our door at the exact same length it was when it left the factory.

Yes, depending on the model year/RPO of your engine. LBZ and LMM can use pretty much any pedal from any GM car or truck from 2008 up that uses the standard Delphi GT150 6 pin connector. Examples of pedals that will work with LBZ/LMM are C6 Corvette and 2010-2015 Camaro.

We do not stock the pedal connector for Van or GTO/G8 pedals or the connector for the LBZ Pickup truck pedal. If your LBZ pedal jumper/connector is damaged, we will install a GT150 connector and you will need to choose from one of the pedals above. We’ll help you make something work with your particular swap in our work order call.

For LB7 and LLY it has a metal bracket that is fairly easy to modify otherwise, some guys use the pedal from a 6.5 Diesel OBS. It can work but just remember it’s a 30 year old pedal so we recommend you start with a known good pedal from the donor first.

A splitter is a much more simple and cost effective solution. Note: we do not recommend more than one device on the port. Multiple devices can cause communication problems between the ECM and TCM. If you need a longer port, extensions are readily available on sites like Amazon and Ebay.

It unfortunately does not work in standalone setups. In the donor truck, Tow Haul was controlled by the BCM in all 2001- current trucks. Since the BCM is not used in a standalone setup Tow Haul is not possible.

We do not supply pigtails for Tap Shift Input. Contact Fleece for LB7 and LLY or Dmaxswap for LBZ Tap Shift Solutions. LMM is not available as the function was handled in the BCM.

That is a completely separate system in the donor vehicle and is not part of a standalone harness. Contact Dmaxswap.com as they have a solution for LB7, LLY and LBZ Electronic Transfer Cases. Otherwise swapping to a manually shifted t-case is popular.

Note: Even Manual Shift T-Cases are completely separate systems. Installer needs to retain the donor truck transfer case/axle harness and use factory schematics on their end to find the signal wire for the 4WD Low signal the standalone harness pigtail needs.

An AC compressor will not stall a Duramax so this feature is not needed in standalone. As for an Idle Up button, we do not support that feature in any of our Duramax Standalone harnesses.

This circuit is not part of a standalone harness. It’s a simple solenoid requiring 12V and ground signals to engage. Many installers use a toggle switch in the cab.

If you are swapping into a vehicle that has the 1969-1994 GM type steering column (with the Automatic shifter on the column) all of those circuits are already in your truck. We do not provide the purple wire that goes to the starter as that is part of your vehicle side electrics and those circuits are completely up to the customer and/or the installer.

LB7 and LLY will have Starter Interrupt and Back Up Lamp Pigtails labeled. 99% of our customers do not need them as those functions are in the swapped vehicle shifter. If you are the 1% you will need to acquire the factory schematics of the switch on the side of the trans so it can be utilized. You will need to use a relay as the switch is not rated for the current requirements of a Starter Solenoid. Determining how to use the Allison PNP (NSBU) Switch for Starter Interrupt is completely up to the installer.

We will return the Compressor Clutch Pigtail in the box. You or your installer can then tie the compressor to your vehicle’s AC management system. Whether it’s an original factory air or a Vintage Air type setup it will work perfectly with the correct fittings and refrigerant charge.

Yes LB7, LLY and LBZ have a cruise function directly in the ECM and every harness is set up with those pigtails standard. It will work with any GM cruise switch on the turn signal stalk of a 1969-1994 GM Type Column. Other alternative switches are available through Rostra and Dakota Digital.

Unlike LS ECM’s the Duramax ECMs do not control Fan Relays. A Derale Thermoswitch is the easiest solution.

Some if not all of the gauges in the donor cluster were controlled by the BCM which is not part of standalone harnesses as a result they cannot be reused.

LB7, LLY and LBZ ECM’s have outputs for Speed and Tach signals. With an aftermarket Programmable Speedometer or Tachometer you can hook up to those signals and program the gauges to work with the Duramax ECM easily. Contact your gauge manufacturer for more info.

For Water Temp and Oil Pressure your gauge cluster will have come with senders which will need to be installed in the Duramax block. Factory Gauge clusters such as the ones in Squarebody Chevys can be used but the installation and connection is completely up to the installer. Note: Only 01-02 LB7 will have a pigtail for Oil Pressure to directly feed a gauge.

The easiest solution is using the OBD port for Gauges that comes on every harness we produce to plug your cluster in and have it pull all of the data directly from the ECM. By far this is the easiest solution for LB7, LLY, and is the only solution for the LMM Family.

Note that Dakota Digital changed their BIM module in 2021 and the part number ending in -2 will no longer work with the LBZ ECM.

To get your engine to run your ECM needs the VATS security feature turned off via EFILive and our recommended tuner is Dmaxswap.com. ECM and TCM Tuning is available from them. Note that the ECM/TCM can be “Tuned” using our harness as a bench harness through the OBD port prior to install in your vehicle.

If you decide not to use Dmaxswap.com then you must vet your chosen tuner carefully. If they are not an Expert Duramax tuner, Standaloneharness.com tech support is limited to helping you confirm the harness is doing its job. Contact us via email for additional details.

Fill in the diagnostic form on the Troubleshooting page with your scanner’s fault codes and live data. All values are read through the OBD port with a scanner only. No volt meter tests or guessing.

For a factory ECM/TCM harness standalone modification rework we do not delete those circuits. Please don’t ask. LB7 California Emission harnesses (Special Glow Plug Relay and EGR) can not be worked on by us. We will only work on the Federal Emissions versions of any Duramax Harness.

Our All New One Piece Standalone LBZ and LMM harnesses are for Closed Course Competition Race Only and are built without emissions circuits. Payment of our invoice is an agreement from the buyer and acknowledges that the products will be used for off-highway closed-course competition use only. Furthermore, the buyer is completely responsible for knowing if the product can be legally used in the jurisdiction where the product is being used, whether on land, water or in the air.