Universal Swap Wiring Guide

Nearly all of the chassis wiring happens at the DME box in the engine bay. After the factory engine harness comes out, the connectors left behind are your interface to the car.

On N55 cars the DME lives under the intake manifold, not in the DME box. The box holds plastic dividers and a few relays and fuses. Once those are out, four connectors remain, and X60001 is the only one whose wires you need: drive-by-wire, radiator fan, key-on power, and the CAN interface. The other pins on X60001 can be used if you want them, but they aren't required for the swap. One tidy approach from a documented build: cut the unused connectors off and terminate the wires with heat shrink to free up space in the box. The N55 notes cover all of it with photos.

On the ECU side, here's the GM E92's X1, X2, and X3 connector layout for reference:

Recommended for every combo: a fuse tap at the cigarette lighter fuse, fuse 8 or 30 depending on year. Key on gives 12V, key off gives nothing, and it doesn't fight the car's sleep logic.

Alternative: E90 connector X6011 pin 6, green/white. Check it with a test light, key on 12V, key off dead. Note this wire also wakes during the car's self checks, so the fuse tap stays the cleaner option.

The terminated harness does not include fuses or relays, so plan the power side yourself: a 20A fused switched-12V feed for the ignition coils and a 15A fused feed for ECU power, both fed through external relays triggered by your key-on source. On the harness 12-pin connector, Pin A is the switched 12V via relay and Pin G is the 15A-fused switched 12V source.

Run the key-on wire to the ignition input of your Gen V swap harness (X1-51 is the run/crank ignition input at the ECU). LT standalone swap harnesses typically have a built-in fuse and relay for ignition power, so check yours before adding another.

Do not use X60001 pin 8 (blue/red) as your key-on source. It fires short bursts of power when the car is locked, unlocked, or a door opens, and those stray pulses aren't good for an ECU long term.

X60001 pin 39 (green/yellow) has been used for the Holley red/white ignition wire on N55 cars.

Source constant 12V from the main jump terminal stud on the passenger strut tower. The large stud is unfused. The small stud is fused by a fusible link above the battery in the rear of the car, so if the small stud is dead, check that link. DO NOT use the small stud for starter or alternator power, it will blow the fuse.

Wire your ECU's main power directly to the battery. N55 cars have a relay at the battery that cuts power to the DME feed after a timeout, and on a Holley that means losing the tune and the TPS autoset. It can be coded out, but direct battery power is the fix, and the Holley manuals tell you to wire it that way anyway.

Most LT swap harnesses put the main power ring terminal at the starter, though it varies by harness. At the ECU, X1-52, X1-70, and X1-73 are the constant battery feeds. Run a proper cable from the large jump stud if your harness needs a separate constant feed.

Ground from any of the main ground studs in the engine bay. Ground both the engine block and the alternator. The LSe90 alternator bracket is powder coated and will not give the alternator a good ground on its own, so run a dedicated strap or sand the coating at the mount. LT brackets that keep the factory aluminum alternator mount won't have the ground issue.

1-wire alternator exciter: if you're running a 1-wire alternator, the exciter wire just needs any 12V ignition signal with a 470 ohm resistor inline. The resistor matters, because without it you can burn out the alternator's voltage regulator.

The green fuel pump wire from the Holley harness is a good option for the exciter signal if you've replaced the EKP with a relay.

The BMW pedal is drive-by-wire, six wires, and they land on the long grey DME connector X60001. Where they go depends on your ECU.

The N55 pedal pins on X60001 differ from N52/N54 cars:

The LSe9x MaxxECU terminated harness includes a 6-pin drive-by-wire pedal connector, so the pedal plugs in rather than getting pinned by hand. The harness install guide covers it.

Your harness should include a 6-pin pedal DBW connector labelled A through F. Car/Corvette and truck harnesses share the same plug but swap pins A and C, and truck harnesses put the two 5V wires in the center positions C and D. Check which donor harness you have before pinning, then use the matching table:

Truck pedal connector (two 5V wires in the center):

Car pedal connector:

There's also a pedal wiring video covering this connector.

The BMW side is the same six pedal wires on X60001. Land them on the Rebel LS drive-by-wire inputs per Haltech's Nexus Rebel LS documentation.

The BMW side is the N55 pedal set on X60001: pins 14 (blue) and 15 (white/yellow) are the signals, pins 24 (yellow/green) and 25 (yellow) are the 5V supplies, and pins 27 (brown/green) and 28 (brown) are the grounds. Land them on the Rebel LS drive-by-wire inputs per Haltech's documentation.

Cross-referenced from our N55 pinout and the E92 pedal mapping, matching each wire by function:

Verify the two pedal signals with a scan tool before first start, since the signal 1 / signal 2 split is the one place a functional cross-reference can land backwards. If you're wiring to the harness's 6-pin pedal connector instead of the ECU pins, the truck/car A-F tables above apply the same way.

The BMW electric fan keeps its factory power and ground. Speed control is one PWM wire from your ECU. The fan wants a 0-90% duty signal, and commanding 100% shuts it off, so cap your duty table at 90%.

The fan signal is X60001 pin 8, black/blue.

On N55 cars the fan signal is X60001 pin 20, black/blue.

Run the fan wire to one of the four grey output wires on the Holley IO harness (Grey/Yellow is B12, Grey/Red is B11, Grey/Black is B10, Grey/Green is B3). Then in the Holley software:

• Add an IO Individual Config from the Toolbox menu, name it (something like BMW FANS), and enable the output.
• Set it as a PWM output, activated above 400 rpm so the fan doesn't drain the battery with the engine off.
• Build the temperature-based duty table. A working starting point: 60% duty at 167 F, 85% at 187 F. Stay at about 90% duty for max fan speed.
• Map the output to the correct pin in the PIN MAP screen to match the grey wire you used.

The fan configuration guide has screenshots of each step.

The terminated harness carries the fan signal on pin D of the 12-pin connector. Build the temperature-based duty table in MTune.

Wire the fan signal to a PWM-capable output on the Rebel LS and build a temperature-based duty table per Haltech's documentation.

Pin X1-59 on the E92 ECU is the high-speed cooling fan relay control, a low-side PWM output. Configure the tune for PWM fan control. Details in the LT wiring guide.

Factory automatic cars need a 12V brake signal at CAS pin 41 before the start button will crank. Without it, the car shuts the ignition off instead of starting. Factory manual cars staying manual skip this.

PRO TIP, COMMON ISSUE: if your car tries to crank the starter without the brake depressed, first check that your brake lights aren't stuck on. The brake switch commonly gets knocked out of adjustment during a swap. It's a magnetic sensor, so push the switch back against the brake pedal until it touches.

Connect X60001 pin 4, the brake light signal, to the CAS pin 41 wire on connector X6031. Pre 03/07 cars have an 8 pin X6031; post 03/07 it's a 12 pin. You're looking for a blue/black wire in the pin 1 or pin 5 position. Make SURE it's the wire that goes to CAS pin 41, you don't want to send 12V into the wrong wire.

Pre 03/07 - X6031

Post 03/07 - X6031

Manual car going automatic: connect the blue/brown wire (pin 18) on X60001 to the blue/red wire (pin 4) on the same connector, then at the clutch switch, join the blue/brown wire to the blue/black wire. That routes the brake signal through the old clutch switch wiring to CAS pin 41.

On factory automatic N55 cars, connect X6031 pin 5 (blue/black) to the brake light signal at X60001 pin 16. That sends the 12V brake signal to CAS pin 41 when the pedal is pressed, and the start button works.

Run a 10ga wire from the larger gauge black wire on X6011, pin 3 on pre 03/07 cars or pin 1 on post 03/07 cars, to your starter solenoid connection.

Pre 03/07 - X6011

Post 03/07 - X6011

Connect X6011 pin 1, the large gauge black wire, to the starter solenoid.

Disable starter diagnostics in the GM tune, or the ECU will complain about the starter circuit it can no longer see.

Required on factory automatic cars to keep the PT CAN network alive. Skip it and odd things happen, most famously windshield wipers that never turn off. On connector X6021, connect pin 1 to pin 3 and pin 2 to pin 4: red to red, blue/red to blue/red.

The E9x runs its fuel pump through the EKP (Electronic Fuel Pump Controller), which lives behind the right-hand side panel of the rear seat. It only speaks factory BMW CAN.

Keep the EKP. MaxxECU controls the factory pump module directly, so you can skip the relay conversion. Details on the fuel system page.

The EKP will not work with a Holley, so unplug it and replace it with a QUALITY 30/40 amp automotive relay. This is a high-current fuel pump circuit, make these connections well.

The EKP has 2 connectors. The smaller connector has two larger gauge wires leading to the fuel pump: brown with stripe (ground) and red with stripe (12V).

On the larger connector, use the only two larger gauge wires: 12V from the red with stripe wire (fused from the factory fuel pump fuse) and ground from the brown with stripe wire. Then wire the relay:

• Pin 85: ground from the EKP large connector brown with stripe, or a ring terminal at the EKP mounting point
• Pin 86: Holley green fuel pump trigger wire (12V when the pump should run)
• Pin 30: 12V fused feed, the large EKP connector red with stripe wire (fused by the factory fuel pump fuse)
• Pin 87: fuel pump positive, the small EKP connector red with stripe wire

The small connector's brown with stripe wire (pump ground) goes to the same ground as pin 85. The EKP connectors can be left disconnected.

Above is an EKP wiring diagram for reference, from a 2007 328i.

The EKP will not work with a GM ECU, so unplug it and replace it with a QUALITY 30/40 amp automotive relay. The EKP has 2 connectors: the smaller one has two larger gauge wires leading to the fuel pump, brown with stripe (ground) and red with stripe (12V); on the larger connector, use the two larger gauge wires, 12V from red with stripe (fused by the factory fuel pump fuse) and ground from brown with stripe.

• Pin 85: ground from the EKP large connector brown with stripe, or a ring terminal at the EKP mounting point
• Pin 86: GM 12V fuel pump trigger wire (12V when the pump should run)
• Pin 30: 12V fused feed, the large EKP connector red with stripe wire
• Pin 87: fuel pump positive, the small EKP connector red with stripe wire

The small connector's brown with stripe wire (pump ground) goes to the same ground as pin 85. The EKP connectors can be left disconnected.

The Haltech CAN box requires the EKP delete, so the pump gets the same relay conversion: unplug the EKP and wire a QUALITY 30/40 amp automotive relay. Pin 85 to ground (EKP large connector brown with stripe, or a ring terminal at the EKP mount), pin 30 to the 12V fused feed (large connector red with stripe), pin 87 to the fuel pump positive (small connector red with stripe), and pin 86 to the fuel pump trigger from the Haltech, configured per Haltech's documentation. The small connector's brown with stripe pump ground goes to the same ground as pin 85.

Early 4-wire to late 3-wire fuel rail pressure sensor conversion. Applies to 2017+ LT1, L83, L86, and L8T Gen V engines using the 3-pin fuel rail pressure sensor. On 2014-2016 engines GM used a 4-pin analog sensor; from 2017 they switched to a 3-pin digital SENT sensor, and the change requires the driver-side fuel rail harness AND the ECU wiring to be updated along with the sensor. Leaving the old 4-pin harness in place, or not moving the signal wire at the ECU, makes the scanner read about 95,050 PSI of fuel rail pressure.

Low-side fuel pressure sensor (recommended). The GM low-side fuel pressure sensor should be used on LT swaps. It comes standard on most LT-powered vehicles under several GM part numbers, uses a 10mm x 1.0 O-ring port, and adapts to NPT with an Aeromotive 65610 adapter, so it drops into an aftermarket fuel line, filter, or regulator. Running it gives you low-side pressure logging, helps diagnose fuel system limits, and keeps the ECU's built-in low-side diagnostics working.

• 5V reference: ECM X1 pin 24 to the sensor 5V reference
• Signal: ECM X1 pin 2 to the sensor signal
• Low reference (ground): ECM X1 pin 8 to the sensor ground

The chassis side of the AC system stays factory: condenser, drier, pressure sensor, and the interior controls. What changes is who engages the compressor, and that runs through your ECU.

The LSe90 CAN box sends the BMW AC button state to the Holley over CAN as a CAN input: the value reads 0 with the AC and max AC buttons off, and 256 when either is on. Note that turning the HVAC fan speed all the way down does not disable the compressor, only the button state does.

• Compressor output: configure a grey-with-stripe Holley wire as a ground output driving a relay that sends fused 12V to the AC clutch, with a time delay so idle and fan speed come up before the clutch engages.
• Pressure input: the factory AC pressure transducer wire (black with a white or grey stripe depending on year) connects to any Holley input wire (white with stripe).
• Idle and fan: command additional idle when the AC is engaged, and set the fan to run at commanded speed as soon as the button is pressed.

The AC control guide and the configuration walkthrough video show the software side step by step.

Pin X1-32 on the E92 ECU is the AC compressor clutch relay control, a ground signal from the ECU. Wire it to a relay powering the clutch. Adapt a GM pressure transducer into the BMW AC line and wire it to X1-6 (pressure signal), X1-21 (5V reference), and X1-22 (low reference). The GM ECU also manages fan speed from AC pressure.

The AC request comes through MaxxECU's native CAN integration with the chassis. The compressor clutch still wants a relay-driven output from the ECU, the same pattern as the other platforms. We haven't published a MaxxECU-specific AC writeup yet, so if you're wiring this combo, get in touch.

The Haltech CAN box transmits the AC button status over CAN to the Haltech ECU. Drive the compressor clutch with a relay from a Haltech output, configured per Haltech's documentation.

The cluster, fans, AC, and half the car talk on BMW's PT CAN bus, which lives on the X60001 connector as a blue/red twisted pair. How your ECU gets on that bus depends on the platform.

On N52/N54 cars the PT CAN pair is X60001 pins 1 and 14.

On N55 cars, locate the blue/red twisted pair on X60001. The N52/N54 pin numbers do not apply here (pin 14 is a pedal wire on the N55), so identify the pair by color. The N55 notes cover the connector.

The LSe90 Holley CAN box bridges the Holley to the chassis: connect its blue/red twisted pair to the X60001 PT CAN pair (located above for your engine), and the 4 pin Holley connectors to the CAN connection on the Holley harness. Check those small 4 pin connectors for bent or missing pins, they break constantly, and plug the keyed 12 pin connector in the right orientation. Never flash Holley firmware with the CAN box plugged in. Setup is in the CAN box configuration guide, and AC control in the AC guide.

MaxxECU doesn't need a CAN box. It speaks the E9x CAN protocol natively, and the terminated harness carries the bus on the 16-pin connector: CAN low on pin 9, CAN high on pin 10, straight to the X60001 PT CAN pair. The install guide has the wiring.

The LSe9x Haltech CAN box bridges Haltech Elite, Nexus, and Rebel ECUs to the chassis over Haltech's IO12 expansion protocol. It installs inline at the BMW DME PT-CAN connection with an included Haltech-specific DTM4 harness, so you don't cut or splice anything. It restores the factory tach, puts coolant temperature on the 335i oil gauge, keeps the dash free of DSC/ABS errors, carries the cruise stalk buttons and wheel speeds to the ECU, and transmits the AC button status. It requires the EKP delete covered in the fuel pump section.

Running the CAN box on an N55 chassis needs a one-time cluster recode. Be sure you understand how to properly code these cars and back up the factory coding before you continue. Use the Protool Android app with any compatible cable; the Amazon K-CAN cable with an adapter works.

In Protool, go to the main menu, then interior, then the cluster.

From there go to coding, then edit coding, then expert.

Change the value shown above. There should be only two options, so switch it to the one not selected, then recode the kombi. The N55 notes carry the same walkthrough.

The LT CAN box sits between the chassis and the GM ECU: blue/red pair to the X60001 PT CAN pair on the BMW side (located above for your engine), CAN low to X1-40 and CAN high to X1-39 on the ECU side (also available at the OBD2 connector). The box mimics the GM BCM and forwards A/C requests and alternator control to the ECU.

The N55 X60001 pinout differs from the N52/N54 table, most notably the pedal wires (pins 14, 15, 24, 25, 27, 28) and the fan signal (pin 20). The N55 notes carry the N55-specific pin details.

Summary of key GM E92 ECU pins. These are the main pins used on an LT swap with the E92/E92A ECU. The small-pin style for E92A connectors is Molex MX64, manufacturer part number 33468-0023, if you need to add terminals.

The BMW pedal pin numbers in this table are for N52/N54 cars. N55 pedal pins are covered in the drive by wire section above.

• Holley swap wiring information (the complete reference this tool summarizes)
• Holley wiring video walkthrough
• CAN box configuration and AC control
• Fan configuration
• Holley official: Terminator X / X Max LS installation and tuning manual (PDF) and the quick start manual (PDF)

• MaxxECU terminated harness install guide
• Fuel system page (EKP control)
• MaxxECU official: documentation hub, GM LS terminated harness page, and manuals and downloads

• Haltech official: Nexus Rebel LS installation and quick start guide
• LSe9x Haltech CAN box
• ECU comparison

• LT swap wiring guide (GM E92 ECU)

• N55 equipped cars (all N55 chassis differences)

• Swap basics: starter wiring and relays
• Reverse lights wiring and coding
• Electrical section of the complete parts list