Before you start
Toyota built the A340E in several versions, and even the USDM MK4 Supra (2JZ-GTE) had more than one. Everything below is based on that Supra unit, which is the one most people are working with. If yours came from something else, the functions will be the same but connectors and pin positions can differ, so confirm against your own transmission before you crimp anything. If you're unsure which version you have, send us some photos and we'll help identify it.
The four connectors on the case
On a left-hand-drive car, three plugs sit on the driver's side of the transmission and one on the passenger side. Here's what each one carries:
| Connector | What it's for | Haltech input or output |
|---|---|---|
| Direct clutch speed (Toyota: NCO) | Input shaft speed, 2-wire VR sensor | SPI, optional |
| Output shaft speed (Toyota: SP2) | Rear speed, 2-wire VR sensor, gives you vehicle speed | SPI, required |
| Valve body plug | Shift solenoids, lockup, line pressure, accumulator, and fluid temp on most units | Outputs plus one AVI |
| PRNDL switch | Tells the ECU where the shifter is | Inputs (six, or one with a converter) |
Some A340Es also have a third speed sensor at the right rear of the case. That one is a Hall effect unit that fed the factory gauge cluster, and the Haltech doesn't need it.
Add a line pressure sensor
The A340E never had a line pressure sensor from the factory. When a standalone ECU is running the show, we strongly suggest fitting an aftermarket one so you can actually see what the hydraulics are doing. A 250 psi sensor such as our 250 PSI TI pressure sensor suits the job.
Wiring the valve body
Depending on year, the main valve body connector has 6, 8 or 10 pins. The functions are the same across them, except that the 8-pin version doesn't carry the fluid temperature signal. On those, temp usually has its own separate plug. Toyota's names for the circuits are:
- S1 and S2: the two shift solenoids that select the gear.
- SLU (sometimes written SUL): torque converter lockup.
- SLT: line pressure solenoid.
- SLN: accumulator back pressure solenoid.
Shift solenoids need high side drive
S1 and S2 are switched on the power side and each one draws around 1 to 1.5 amps. That rules out ordinary low side outputs. If you have an Elite 1500 or 2500 with spare DBW outputs, those can drive the solenoids directly. Otherwise, use a low side DPO to switch a relay that supplies 12 V to each solenoid. If you drive the solenoids directly, set those outputs to high side in software and make sure each can deliver 1.5 amps.
Lockup, line pressure and accumulator are ground switched
SLU, SLT and SLN are all switched to ground, so any free DPO or unused injector output can run them.
Fluid temperature
If the temp sensor lives in the valve body, run it to a spare AVI and turn on that input's pull up in software. On units where the sensor has its own 2-wire plug, wire it the same way. You can also fit a separate sensor in the pan if you'd rather measure there. For more on reading thermistors, see our guide to diagnosing temperature sensors.
Shifter position: six wires or one
The factory range switch sends a separate 12 V signal for each position. You can wire all six to spare inputs, but that eats a lot of I/O. The tidier answer is a converter that turns the six signals into one analog voltage, like the PRNDL signal converter for the A340. Then only one AVI is used.
In NSP, open the Transmission node and pick your selector position type:
- Voltage Input if you're using a converter. Then go to Selector Position, enable Park, Reverse, Neutral, Drive, 2 and Low, and calibrate the voltage and tolerance for each by moving the shifter through every position. Your voltages will be specific to your converter.
- One per position if you wired the six signals directly. Assign each input on the wiring tab.
To prove it works, add a number display for Gear Selector Position and watch it follow the shifter.
Base transmission control settings
Haltech's transmission control has far more features than you need to get moving. These are the tables that matter for a first drive:
| Setting | What it does | Our advice |
|---|---|---|
| Auto Mode Shift Points | Road speed (MPH) for each upshift and downshift, against engine demand | Our preferred way to tune shifts. Rows like 1->2 are upshifts, 2->1 are downshifts |
| RPM Shift Point | Forces a shift at a set RPM | Treat it as an over-rev safety net, or use it as a WOT shift table |
| Shift Inhibit | Blocks a shift, usually a downshift at too high an RPM | Depends on your ratios. Start low and raise it carefully |
| Shift Duration | How long a shift takes, used for pressure control during the change | Start long if unsure, then measure it from logs |
| Output for Gear | Manual solenoid mapping | Not used once you pick a specific transmission type |
| Wiring | Assigns the S1 and S2 outputs | Set both to high side |
Holding the shifter in 2 or Low
To make the 2 and Low positions behave, add selector position as the 4D axis on the shift point table. For those positions, fill the upshift cells you want to prevent with maximum values so the ECU never asks for them. The RPM Shift Point can still force an upshift at the limit, which is what you want as protection. A manual or paddle mode, or a sport mode with sharper shifts, gets added to the same 4D axis and tuned separately.
Measuring shift duration
Log the transmission control shift progress along with engine RPM. The time between the shift starting and RPM dropping and settling at the new gear is your real shift duration.
Line pressure and accumulator
The A340E's SLT solenoid is a bleed type running at 300 Hz. More duty bleeds away more pressure, so 100% gives you the lowest line pressure and 0% the highest. That's backwards from what many people expect, so double check it before your first drive.
Of the three line pressure control methods, open loop is the easiest place to start: you set the duty directly in tables for in-gear, during shifts, and a fluid temperature correction. More power generally needs more pressure, which means less duty. Too much pressure makes cruising shifts harsh, while too little lets the clutches slip, which is what kills these transmissions behind a built 2JZ.
The SLN accumulator solenoid also runs at 300 Hz and works the same way. It exists to soften shifts, but once you're tuning shift pressure with the line pressure tables it adds little. You can run it with a simple table and leave it at that.
Torque converter lockup
Lockup is for cruising in 4th, not for heavy load. Never let the converter lock while you're making big power. The key settings in the torque converter function are:
- Lock point: the road speed where it locks once every other condition is met. Around 45 MPH is a sensible start, then adjust for your gearing, tire size and normal cruising speed.
- Unlock point: the speed where it releases as you slow down. Set it 5 to 10 MPH below the lock point so it doesn't cycle.
- Lock duty cycle: the PWM that holds the clutch engaged without slipping. Watch input and output speed in logs to confirm it's truly locked.
Flat shift for cleaner shifts
A short torque reduction during each shift makes the A340E shift firmer without being hard on it. On an automatic you don't use the flat shift active time, because transmission control triggers the flat shift itself.
- Link option: turn on the link to transmission control and choose to start the cut after the shift begins. That's what we use on the A340E.
- Link delay: the time from the shift command to the gear actually changing. Measure it by logging the shift request and watching for RPM to drop.
- Mode: Timed gives you its own duration table (RPM and TPS axes are common). While active uses the link delay table instead, and the trigger must be set to triggered by the transmission control function.
- Reduction type: we prefer ignition cut plus retard, ramped back in together, for the smoothest result.
The cut percentage table sets how many cylinders are dropped, the retard table how much timing is pulled, and the recovery time how quickly both are returned. Bringing torque back instantly makes the shift harsh and wears the transmission, so ramp it in at part throttle. At full throttle, a near-instant return is normal.
Troubleshooting
| Symptom | Usually |
|---|---|
| Stuck in one gear | S1/S2 outputs misassigned, not set to high side when driven directly, or not able to supply enough current |
| Harsh shifts when cruising | Too much line pressure (duty too low), or torque returned too fast after a shift |
| Flare or slip between gears | Not enough line pressure (duty too high), or shift duration too short |
| Gear selector reads wrong | Converter voltages not calibrated, or tolerance windows overlap |
| No vehicle speed | Output shaft (SP2) sensor not wired to an SPI or not configured |
A340E FAQ
Do I need the factory transmission ECU?
No. The Haltech drives the solenoids and reads the sensors itself once it's wired as above.
Can I add paddle shifters?
Yes. Add a manual mode to the 4D axis on the shift point table and use shift inhibit to block downshifts that would over-rev the engine. We're happy to help plan it in a free consultation.
Is this the same process as other automatics?
The software side is similar. For a GM example, see our 4L80E with an IO12 guide.
