Plug-in-Play: Installation of standalone LS replacement harness (2023)

Trading an LS vehicle is like putting together a puzzle, but you don't have all the pieces to begin with. It takes a lot of research to figure out what you need, but don't worry, you can find almost anything on the secondary market. Putting an engine into a vehicle is usually an easy task, but what next? Well, you need to understand the fuel system, cooling, exhaust and finally wiring, which we will focus on in this article with the help of BP Automotive owner Bill Hillock.

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Installing a standalone LS replacement harness is very easy if you take your time.

What you need to know

Before ordering a belt for your project, you need to know some information about your engine and gearbox. For example, if you can tell the year of the drivetrain, whether it is drive-by-wire or drive-by-cable, what injectors you have, whether it is generation III or generation IV, etc. this will be very helpful in kit order. And while GM has done a great job with the modularity of the 3rd and 4th generation LS engines, there are a few differences between them that need to be identified to ensure you choose the right one. But don't worry if you don't know all the answers because we dodetailed articlewhich allows you to search for any information.


we visitedBP Automotive websiteand ordered a Gen III Drive-by-Cable engine control kit for the Suburban. Unique to this system is an independent custom wiring harness, pre-programmed GM Power Control Module (PCM), PCM Socket, Delphi Mass Flow (MAF) Sensor and two Delco AC Oxygen Sensors. With this package we got everything we needed without having to go to the auto parts store at the last minute.

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Our BP Automotive wiring harness had everything we needed to install, including the ECU, ECU bracket, oxygen sensors, MAF sensor and a standalone wiring harness.

Our package arrived within a few days of placing the order. We were happy to unpack it and check the harness. The first thing we noticed about BP products is that each thread has a label. Then we remembered that we had chosen a braiding loom with a stopper, and it was worth the $75 upgrade. This nylon mesh loom looks and feels much better than the plastic loom used in most standalone devices. We also received a very detailed manual and a document stating that the harness passed quality control along with the harness, sensors and PCM. And while the strap looks very nice, there's more to it than just looks.

Hillock said: “Our harnesses are manufactured entirely in-house, giving us full control over the quality of our product. We only use TXL cross-linked wire to OEM standards and terminate connections with specialized hand tools and other manufacturing equipment. All BP Automotive belts are computer tested to ensure no human error. So we know that if we have a starting problem, it's on our side, not BP Automotive.

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  • Plug-in-Play: Installation of standalone LS replacement harness (4)
  • Plug-in-Play: Installation of standalone LS replacement harness (5)

let's start

Technically, you can install a standalone wiring harness while the engine and transmission are in the vehicle, but we do not recommend this method. In our opinion, it is much better to carry out the replacement as complete as possible before starting the installation process. Items such as manifolds, exhaust pipes, oxygen sensor location, and even mass air flow (MAF) sensor location can determine the routing of some wiring. And while we love working on vehicles, going back and re-routing is never welcome.

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Please read the instructions before starting the installation process. This will answer about 95 percent of any questions you may have before starting.

When we started this project, the replacement was a '91 Suburban. it was about 95 percent complete. The fuel system was hooked up, the radiator and fans were fitted, the exhaust system was fitted, even the engine had all the trim including the ignition coils and intake manifold. So there is only one thing left for us to do, and that is to fasten our seat belts. But take your time. Hillock said: "People are excited, they take the strap out of the box and try to fit it right away. Slow down, familiarize yourself with the seat belt, then read the instructions. Content is your friend, and the manuals answer 99 percent of the questions we receive."

PCM installation

We usually prefer to mount the PCM in the vehicle. They can usually be placed behind the dashboard or under the driver or passenger seat to hide the unsightly device. However, Suburban fought with us for this idea. Behind the control panel there was no space due to ventilation ducts, and shell sockets also did not provide enough space for the device. Our only option was to mount it in the engine bay. We set out to find the perfect spot for the PCM in the GM mount around the engine bay, but we had one problem: the PCM mount needs to be on a flat surface, and despite the Squarebody's square exterior, the engine bay is quite round.

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Ironically, finding a home for PCM was the hardest part of the process. To get an idea of ​​where we could mount the PCM, we routed the wiring harness in the engine bay. Unfortunately, the passenger side fell off due to the battery and air conditioning. We also looked at the radiator bracket, but couldn't because the light plugs were sticking out, leaving us with only one option - the area in front of the driver's side wheel arch.

We recreated the PCM in a new location and made sure we had enough space to put the stripes where they needed to be before we drilled holes in the inner fender, making it durable. It is worth noting that the PCM carrier is plastic; Although some aftermarket companies offer metal brackets, GM always uses a plastic bracket to ensure that the PCM is connected to the intended source and not to the chassis, which can cause problems.

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  • Plug-in-Play: Installation of standalone LS replacement harness (10)

Plug it in

After installing the PCM and fuse block, we turned our attention to the wiring harness. BP Automotive simplifies the installation process by labeling each wire. The only thing that can cause confusion is the wires labeled "Bank 1" and "Bank 2". Row 1 refers to the driver's side of the engine, while row 2 refers to the passenger side. Each group has a coil connector that connects to the coil pack and four fuel injection connectors on each side of the engine.

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Once the ECU was fitted, we started running the wires to where they needed to be routed. The process may seem a bit tedious at first, but it's not bad.

After sorting out banks one and two and connecting them to the coils and injectors, we proceeded to attach the idle air control (IAC) valve and throttle position sensor (TPS) to the throttle body. We then fitted two grounding points to the rear of the driver's side cylinder head and connected the knock and camshaft position sensors to the rear of the engine. Next, we routed the power cord connected to the starter motor, the oxygen sensor wires, and the crankshaft position sensor wire along the top of the gearbox, making sure to keep them away from the manifold.

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The only other wires that need to be connected are the transmission wires and air conditioning wires. We ran the transmission wires through the tunnel to clear the outlet and connections. Next, we connected the transmission connector and the speed input and output wires. If you have a 4L80e or 4L60e with a transfer case, you will need longer wires to the input speed sensor as the output sensor is in the transfer case. Luckily, BP had an extension cord that allowed us to connect the output speed sensor in the transfer case, so we didn't have to cut wires. And if you need something special, such as longer cables or re-routing, let the manufacturer know before ordering.

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BP Automotive can match your belt to any gearbox you have.

“Because we manufacture the tires in-house, we can adapt the design to the customer's needs if necessary,” explains Bill. The only exception is a change to where the "trunk" of the wiring harness exits the passenger side engine. We still reverse mount the 4150 style throttle body and intake manifold bands. We can add housings for ethanol content sensors and other sensor displacements. Just send us an e-mail and we will easily give you a price and delivery time. Custom requests usually require an email to ensure we know your specifications.

Air conditioning

The factory ECU needs a signal from the high pressure line when the A/C system is on to keep the engine idling and turning on the cooling fan. In our application, we used an aluminum welded joint from BP Automotives and a GM pressure sensor. BP also offers other types of connectors and products to facilitate the installation process. However, it is very important that this part is in place for the system to function properly.

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If you are going to turn on the A/C it is very important to make the correct connection so that the ECU knows when to turn on the cooling fan. BP Automotive offers various types of connectors for air conditioning systems. Weld the anchor shown here to the aluminum pipe on the high pressure side.

Coolant and oil pressure sensors

The BP wiring harness does not come standard with a factory oil pressure sending module connector, but you can ask the company to add one if needed. In most cases, the oil pan is used as a transport unit for factory or aftermarket gauges. But if you have a set likeDigital Dakotagauge with an OBD II/Can interface module, consider adding the oil pressure wires back to the wiring harness. Since the OBDII/CAN interface takes data from the OBDII port to display gauges, adding wires means less running to the cab. The same applies to the coolant sensor. Since we are using Dakota Digital gauges and OBDII/CAN interface, we do not need to add an additional water temperature sensor to the mixture as the wiring harness has it. However, this is not a problem, as there is a plug above the head on the passenger side that can be removed and replaced, allowing the connection of two temperature sensors.

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We connected the driver's side cylinder head to the coolant temperature sensor. You can also use the second port on the back of the passenger's head.

Mass air flow sensorR

The MAF (MAF) sensor wires are quite long, which allows plenty of room to route the wires to the sensor. However, they are aimed at the other (passenger) side of the engine. Since the battery in our truck is on the passenger side, we were forced to move the battery or throw out the air filter on the driver's side. In retrospect, we should have informed BP of this and they could have made this adjustment for us. The problem is that the wires are dangerously close to the poly V-belt, which can cause problems on the road if we are not careful.

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In this photo you can see how close the MAF wires are to the belt. You want to make sure they're secure and don't snag on your belt or accessories.

Party packages

Until now, our harness was simply plug and play. But you have several wires to connect, labeled bundles 1, 2 and 3. Keep in mind that we like to use non-insulated connectors and heat shrink tubing to connect wires. This method ensures a strong and visible connection, and the adhesive contained in the heat-shrinkable layer protects against moisture. But you can use insulated connectors or solder to get the job done. Just take your time and make sure everything is ready before cutting and connecting the wires.

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We connected the wire with a non-insulated connector, and then we sealed the connection from the elements using a heat shrink tube with glue.

package one

Package one contains a two-wire connector that will start our engine. Two ignition circuits and fuel pump have been replaced. Since there is already a fuel pump relay in the fuse box, we only had to connect one wire. We found the existing fuel pump wire in the engine bay and connected it together.

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Next on our list was the ignition wire, which we routed through the cabin. Switch ignition means that no current flows through the wire until the ignition switch is turned to the "on" or "run" position. This wire in the factory wiring harness can be easily found by the indicator light. Once we found the right one, we connected it to the pink/black wire in the BP harness.

Package two

Bundle 2 consists of four wires for electric fans. The BP manuals contain a diagram showing how to connect them in a configuration with one or two fans. In addition, one or two relays are needed, depending on the chosen route. We used two GC Cooling fans and their relays and wiring harnesses, then spliced ​​the BP wiring harnesses together for a clean install. BP also offers its own set of relays color coded to match the wires in the wiring harness for easy connection.

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Each wire in the harness is clearly marked for quick and easy identification.

Package three

The third bundle has the most wires and all of them should be in the vehicle. Since our ECM was mounted in the engine bay, we decided to unhook the OBDII module to route the cable through the stock grommet in the firewall. Of course, we could have drilled a larger hole, but we prefer to use an existing hole where possible. If you plan to disconnect the OBDII port, be sure to label the wires and their location. This is extremely important and can cause serious problems if done incorrectly. Fortunately, the connector has numbers to make the process easier.

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We disassembled the OBD II connector to route it to our Squarebody.

After reassembling the OBDII port inside the truck, we routed the rest of the wiring to the cab. This wiring kit includes tachograph output, speedometer, fault indicator and brake switch. The cable for tachograph and speed is simple, because it is connected to the inputs of electronic counters. The fault indicator wires connect to the check engine light so you'll be notified if the ECU detects a problem. However, if you try to use an LED bulb, it will always stay on and you will need to connect a resistor to make it work properly. BP offers resistance if you need it, which we did.

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The last item to connect in kit 3 is the TCC/brake switch required for the 4L60 and 4L80 transmissions. This switch tells the ECU when the brake is applied so it knows to unlock the torque converter. We used part number TCC-001 and replaced the square brake switch on the body. This switch has two sets of connections: one for the brake lights and one for the ECU.

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The TCC/Brake switch informs the ECU that the brake is applied and allows the torque converter lockout to be released.

Get ready for a mess

We spent several hours on this installation and now our vehicle is ready to start. However, since it has a camshaft, heads and larger injectors, we still need a little more tuning before it's ready to hit the road, but the LS swap is 100 percent complete.

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Everything is packed and we are almost ready to leave.

When you are ready to install a new belt, we recommend that you read all the instructions. This will save you a lot of time and possibly headache during the process and you won't have to think too much about it. "Although it may seem too simple or something is missing, the installation of the BP Automotive belt is extremely easy," said Hillock.





What is an LS standalone harness? ›

A standalone harness is used just for engine control, i.e. the basics. Compared to a factory wiring harness, a standalone harness is a bit smaller and features less connections. This is because it is not intended to run a lot of the additional options, like cruise control or fuel management.

What does an engine wiring harness consist of? ›

An engine wiring harness is constricted wires, cables, terminals, and connectors controlling a vehicle's electrical system. It relays electrical power and control information to components such as batteries, alternators, fuel injectors, fuses, audio systems, blower motors, fuel injectors, and computers.

Where is an engine wiring harness located? ›

The wire harness carries the current from the engine back to the fuse box, usually found under the driver's side dashboard.

Is the wiring harness part of the engine? ›

Before now, cars were solely mechanical and could run without electricity. But it'll be a miracle to run a modern car without electricity. For this reason, auto wiring harnesses are a crucial part of any car engine. Electrical current won't reach the car's different electrical components without them.

What does LS stand for on Chevy Motors? ›

LS stands for “luxury sport” and is what is featured in the names of most of the base models in the Chevy lineup. You'll find the LS label in certain trims of the following Chevy models: Chevy Trailblazer. Chevy Trax.

Can a car run without an engine harness? ›

Your vehicle needs more than your engine, and it requires a lot of electricity for certain things to function, like your radio or lights. Beyond that, your battery, starter, and even your alternator run on power, which is provided by the engine. Without an engine wiring harness, you couldn't start your vehicle.

How many wires are in a harness? ›

Standard Automotive Wiring Harness Circuits. The most basic automotive wiring harness will typically contain 12 "circuits", or lengths of wire for a specific purpose, with a designated fuse holder in the fuse block for each circuit: Radio. Wipers.

What is a harness plug? ›

Connectors are the electro-mechanical devices used to form a continuous electronic signal to connect wire harnesses to a power source or circuit. On a basic level, connectors consist of male-ended plugs and female-ended jacks that can be joined together to relay an electronic signal.

What is a wire harness plug? ›

Wire harness connectors provide an uninterrupted electronic signal between a wire harness and a power source. Plugs are typically male, while jacks are usually female. Other than that, connectors may differ broadly in size, shape, and dimension as needed by the intended application.

How many hours does it take to install a wiring harness? ›

In other words, installing a wiring harness could take as little as an hour, as long as 20 hours, or longer if complications arise. Despite the ambiguous answer for timing, dropping in a wiring harness is a significantly faster and safer way to install electrical assemblies compared to placing each wire one by one.

What gauge wire is used in engine harness? ›

Standard automotive primary wire is 18 gauge. This is good for signal wires, but not for hi-current applications. If you replace that section of wire with a piece of 18 gauge, it could cause a fire. Instead, you need to match the original wiring size.

How do I know what wiring harness I have? ›

Most wiring harnesses will have identifying part numbers in different places on the harness. The number will be on a piece of tape wrapped around the harness. If you cannot find any, then you will have to identify it by what it is connected to and the colors of the wires. This way it can be isolated and identified.

Are all wiring harnesses the same? ›

At the end of the day, there are many different off-the-shelf wire harnesses and cable assemblies out there. The difference is these can be lower quality and still require significant time and effort to make them fit a system.

Can an engine wiring harness be repaired? ›

Old Guy. Damage, rodent or otherwise, is repairable with good quality splices and the proper technique. The biggest issue with the engine wiring harness is that depending on where the damage is, in order to do a good repair you have to remove the wiring harness. Removing a wiring harness is not a trivial task.

What is LS wiring? ›

Ls means live supply so this is where you put 230v or 24v into the switching circuit on the device. Lr is the switch live return back to operate your system. These connections are electrically isolated from the main board to prevent back feed.

What are the different types of wiring harness connectors? ›

They may be crimped connections, soldered connections, press-fit in a ribbon connector or even wire-wrap. They also come in many shapes such as ring, spade, hook, quick-disconnect, bullet, butt terminals and flagged.

What is LS vs Coyote? ›

In general, the Coyotes include more moving parts, which means that they rev higher and withstand blindingly high RPMs, if that is what you need for your hotrod project. GM's LS engines are smaller, which makes them simpler to install, and they typically include fewer moving parts overall.

What is the difference between LS and LT crate engine? ›

When asked to give reasons for choosing an LT over an LS, Mike Lough said, “The short block components in an LT are stronger from the factory versus most LS. Many of them are 6.2L, which is a desirable size for the enthusiast to swap into a muscle car or an old truck restoration.


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