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Auto APPLICATION 1UZ VVT-i WIRING

What you can Expect:

AUTO Application 1UZ-FE VVT-i Wiring – Supported Platform

The 1UZ-FE VVT-i is a significant upgrade over the non-VVT 1UZ-FE, offering more power, better efficiency, and modernized electronics. We specialize in converting the OEM harness for these engines, ensuring a seamless, plug-and-play installation into any vehicle.

What You Can Expect from Our Service

✅ Thorough Harness Inspection & Refurbishment
Our process starts with a complete cleaning and inspection of the harness. During this stage:

We remove any unnecessary wiring that is not needed for the standalone setup.
If required, we add missing components to ensure full functionality.
We inspect and replace brittle or broken split tubing to ensure long-term durability.

✅ Standalone System Conversion
We integrate a fuse box into the harness and reroute the original body wiring into the harness itself, creating a clean, unified standalone system.

✅ Simple Vehicle Integration with a Client Plug
To make installation easy, we provide a client plug with a pigtail connector, allowing you to wire the engine into your vehicle effortlessly. This plug includes:

Essential engine start-up wires:
- Ignition
- Start signal
- Fuel pump power supply
Dashboard signals:
- Rev counter (tach signal)
- Engine temperature sensor
- Charge light
- Oil pressure light
Depending on the original harness sent in, additional signals may include:
- Air conditioning compressor electric clutch trigger

✅ Automatic Transmission Support
For automatic configurations, we include an additional client plug dedicated to transmission functions:

Park
Neutral
Drive
Overdrive
Three
Two
Low
Cruise control wiring is also included as standard, even if you don’t plan to use it.

✅ OBD2 Diagnostics Integration
Unlike the outdated OBD1 system in non-VVT models, the 1UZ-FE VVT-i comes with OBD2 support, allowing you to:

Read live data from your engine
Diagnose issues quickly using an OBD2 scanner
Improve troubleshooting and tuning

Pricing

💰 Base Price (Automatic Configuration): $690
(This price covers all wiring modifications but does not include connector replacements or immobilizer bypass.)

💰 Immobilizer Removal: $90
(The immobilizer must be removed for the ECU to function properly in a swap.)

💰 Connector Replacements: Priced separately based on individual harness needs.

Connectors vary from harness to harness, so we inspect before finalizing costs.
On average, connectors cost around $6 each installed.

Testing & Documentation

Once the harness and ECU modifications are completed, we:
✅ Install your harness onto one of our test engines
✅ Conduct a full walkthrough and test-run video for your records
✅ Provide a shared folder containing:

Welcome pack
Client plug pinouts
Detailed images of the harness
Shipping information

This ensures complete transparency, giving you peace of mind that your system is wired correctly and tested before shipment.

Why Choose the 1UZ-FE VVT-i?

🔹 More Power & Efficiency – VVT-i improves low-end torque, fuel efficiency, and overall performance compared to non-VVT models.
🔹 Coil-on-Plug Ignition – Eliminates the distributor and plug wire system, improving reliability and tunability.
🔹 Modern OBD2 Diagnostics – Allows for live data monitoring, better troubleshooting, and easy tuning.
🔹 More Reliable ECU – Unlike non-VVT ECUs, the VVT-i ECU is less prone to failure and does not require rebuilding.

Final Notes

We take great pride in our work, ensuring that your 1UZ-FE VVT-i harness is built for long-term reliability and performance. If you have any questions or need more details about ECU reliability, please refer to the “1UZ VVT-i OEM ECU Reliability” section.

For a clean, hassle-free, and tested wiring solution for your 1UZ-FE VVT-i swap, contact us today to get started! 🚗⚡

An example of what you will receive in video:

1UZ VVT-i Automatic Application Test Run Video (youtube.com)

1UZ-FE VVT-i OEM ECU Reliability

The 1UZ-FE VVT-i ECU is a reliable and cost-effective engine control unit that rarely requires replacement. When issues do arise, they are typically caused by physical damage or water exposure, rather than internal failures like those found in older non-VVT ECUs.

💰 Cost of Replacement:

Used ECUs can be found as low as $50 from junkyards
Online sources such as eBay often list them for around $70, often with free delivery

Understanding the Immobilizer System

Virtually all 1UZ-FE VVT-i ECUs come with an immobilizer, which must be addressed before the ECU can function properly in a swap. You have two options:

Immobilizer Bypass ($90) – We remove the immobilizer, allowing the engine to run in any vehicle without security restrictions.
Keep the Immobilizer Functional – If your setup includes the original key, transponder, and immobilizer system, we can wire it in accordingly.

ECU Limitations & Handling Diagnostic Trouble Codes (DTCs)

🔹 Read-Only Memory (ROM): The 1UZ-FE VVT-i ECUs cannot be flashed or reprogrammed, meaning any DTCs related to missing components (e.g., automatic transmission) will remain unless addressed through hardware modifications.

🔹 How to Handle Transmission DTCs in Manual Swaps:

Option 1: Simply ignore the automatic transmission DTCs. These do not affect engine performance.
Option 2: Use a transmission emulator, which tricks the ECU into thinking the transmission is still present. However, this may also introduce EVAP and secondary O2 sensor error codes, which would need to be ignored.

Our recommendation is to disregard transmission-related DTCs when doing a manual swap, as they do not impact drivability or engine performance. This approach provides the smoothest and most hassle-free integration for your 1UZ-FE VVT-i swap.

Back to Wiring Services

Additional Information

The Toyota 1UZ-FE 4.0L Engine: Specifications and Reliability

The 1UZ-FE, the first in the UZ engine series, was a 4.0-liter V8 gasoline engine featured in Toyota and Lexus luxury and sports cars from 1989 to 2002, before being replaced by the 3UZ-FE engine. It succeeded Toyota's older V family engines, which were used from the 1960s through the 1990s. The 1UZ-FE engine is characterized by an aluminum cylinder block with thin cast-iron cylinder liners and a 90-degree angle between the cylinder banks, offset by 21 mm. It features six main bearings and a forged steel crankshaft with eight counterweights. To minimize rotational mass, it includes lightweight forged steel connecting rods, aluminum pistons, and induction-hardened connecting rod pins. In late 1994, the 1UZ-FE received updates such as a lighter crankshaft, connecting rods, shorter piston pins, and redesigned pistons. Its quiet and smooth operation is largely due to liquid-filled compound engine mounts. In 1997, it was further refined with a more rigid cylinder block to enhance quietness.

The 1UZ engine is engineered more like a racing powerhouse than your typical road car engine. It's equipped with an eight counterweight crankshaft, and its components are designed to be lightweight. The bore and stroke dimensions are almost perfectly square, which is quite unique. But the standout feature has to be the DOHC 32-valve aluminum cylinder heads. This is a stark contrast to the older V8 engines, which usually had a single camshaft in the cylinder block and OHV heads with just two valves per cylinder. The 1UZ-FE, on the other hand, features two camshafts per head—one for intake and one for exhaust, with four valves for each cylinder. The intake camshafts are belt-driven, while the exhaust camshafts are gear-driven by the intake ones. Instead of using hydraulic lifters, this engine uses solid aluminum alloy valve lifters and steel outer shim type valve adjusters. Initially, the valve stem diameter was 6.0 mm for both intake and exhaust valves, with the intake valves being 33.5 mm in diameter and the exhaust valves 28.0 mm. But in a late 1997 update, the valve diameters were increased to 34.5 mm for intake and 29.0 mm for exhaust, and the stem diameter was reduced to 5.5 mm.

The initial design of the 1UZ-FE engine showcased a simple ignition system, comprising two distributors along with two ignition coils. This engine initially employed multi-port fuel injection (MFI) technology until 1994, which was then upgraded to sequential multiport fuel injection (SFI). The Non-VVT-i variant came with a mechanical throttle body and was fitted with an aluminum intake manifold. Additionally, it featured an Exhaust Gas Recirculation (EGR) system, which was responsible for redirecting a portion of the exhaust gases back into the combustion chambers. These gases were cooled by the engine's coolant system located at the rear before re-entry. However, the EGR system was phased out in 1997. As for the exhaust configuration, it boasted stainless steel headers and monolithic-type three-way catalytic converters.

Engine Specifications:

- Manufacturer: Tahara plant

- Production Years: 1989-2002

- Cylinder Block Material: Aluminum

- Cylinder Head Material: Aluminum

- Fuel Type: Gasoline

- Fuel System: Fuel injection

- Configuration: V

- Number of Cylinders: 8

- Valves Per Cylinder: 4

- Valvetrain Layout: DOHC

- Bore: 87.5 mm (3.44 in)

- Stroke: 82.5 mm (3.25 in)

- Displacement: 3,968 cc (242.1 cu in)

- Engine Type: Four-stroke, naturally aspirated

- Compression Ratios:

- 10.0:1

- 10.4:1 (since late 1994)

- 10.5:1 (since 1997 for VVT-i engines)

- Power Output:

- 251-261 hp (191-195 kW) at 5,400 rpm (non VVT-i)

- 290-300 hp (216-224 kW) at 5,900-6,000 rpm (with VVT-i)

- Torque:

- 260-269 lb-ft (353-365 Nm) at 4,400 rpm (non VVT-i)

- 300-310 lb-ft (407-420 Nm) at 4,000-4,100 rpm (with VVT-i)

- Engine Weight: 364 lbs (165 kg)

- Firing Order: 1-8-4-3-6-5-7-2

- Engine Oil Weight: 5W-30

- Engine Oil Capacity:

- 5.0 liters (0.3 for oil filter) for 1989-1994 models

- 5.1 liters (0.3 for oil filter) for 1994+ models

- Oil Change Interval:

- 6,000 miles (10,000 km) or 12 months for 1989-1994 models

- 9,000 miles (15,000 km) or 12 months for 1994+ models

- Applications: Lexus GS 400, Lexus LS 400, Lexus SC 400, Toyota Aristo, Toyota Celsior, Toyota Crown, Toyota Soarer