Guide · Haltech

EGT on Haltech

Haltech's Nexus and Elite ECUs read an exhaust gas temperature amplifier on an analog voltage input (AVI), set up as Exhaust Gas Temperature 1 in NSP with a volts-to-temperature calibration. This guide covers which inputs work, the wiring, the NSP setup, and diagnostics and cylinder protection.

Checked against Haltech's NSP support articles and ECU pinouts, September 2026. Some of those articles are several years old, so a label can differ slightly.

00What you need

• A Haltech Nexus or Elite ECU with a free AVI, and NSP connected to it. An Elite still on the older ESP software needs Haltech's free update to NSP first.
• An EGX5 for the ECU's 5 V sensor supply, or an EGX12 for switched 12 V. Either one needs an ungrounded Type K probe; the kits include one.
• A multimeter.

01Pick an input

Use an analog voltage input, an AVI. AVIs read 0–5 V. Most have a selectable 1 kΩ pull-up to 5 V, and it has to be off for an EGX.

• How many: Nexus R5 has 23 AVIs, R3 and S3/S2 have 11, T2/T1 have 5, Rebel LS has 2, and Rebel JZ has 3 (AVI 1 is pre-pinned for the starter switch). Elite 1000, 1500, 2000, 2500 and 2500 T have 10, and Elite VMS has 5.
• Elite 550, 750 and 950 have only two AVIs, AVI 1 and AVI 3, marked for an O2 sensor and MAP.
• Elite 1000, 1500, 2000 and 2500: AVI 7–10 come pre-labelled for air temp, coolant temp, MAP and TPS.
• See what's free in Setup → IO Report.

02Wire it

• The 5 V supply is shared. R3 and S3/S2 have a single 5 V pin and a single ground pin, and several Elite models limit 5 V to 100 mA. The EGX5 draws under 2 mA.
• EGX12 supply: Elite pinouts have no switched 12 V output. On Nexus R5, R3 and S3/S2, a spare half-bridge output can be set to give a steady 12 V. On T2/T1, share the ECU's own fused, relay-switched 12 V feed to pin A26. Otherwise use a fused switched 12 V feed.
• Use the sensor ground, not chassis. Every 4–5 mV of ground offset reads as about 1 °C.
• An EGX5 goes on a 5 V sensor supply only, never 12 V. It has no reverse-polarity protection either, so check red and black before you power up.
• Both outputs stay near 5 V, even in a fault. The EGX5 can't rise above its own 5 V supply, and the EGX12 is capped at about 5.3 V.

Probe side

• Kit: the probe plugs into the mini-K socket.
• Module only: yellow to the probe's +, red to −, spliced right at the module.
• Need more reach? Extend from the probe end with Type K extension wire, never copper.
• Ungrounded probes only. An ohmmeter from either lead to the sheath should read open.
• Mount the module somewhere cool, on the cabin side of the firewall or an inner fender: under 50 °C for an EGX5, under 100 °C for an EGX12.

03Set it up in NSP

1. In NSP, tick EGT 1 under Exhaust Gas Temp on the Sensors page, or enable it under Enable Disable Functions.
2. Open Sensors → Exhaust Gas Temperature 1 → Wiring. Set Input Type to Analogue - Voltage, pick your AVI with Exhaust Gas Temperature 1 Input → Edit, and set Pull Up to Disable. If it's your only EGT sensor, set Position to Unassigned.
3. Open the Exhaust Gas Temperature 1 calibration and replace the example values. Set the two columns to 0.000 V = 0 °C and to your model's full-scale point from the table below.
4. If NSP highlights Reboot Device in red, reboot the ECU.

Haltech's help screenshots show a calibration of 0.75 V = 0 °C and 4.50 V = 1250 °C. That's only an example; an EGX starts at 0.000 V = 0 °C.

NSP shows °C or °F according to Preferences → Units Options. If EGT 1 is already used, set up the next free EGT channel the same way.

A dash means past that model's range.

04See it and log it

• Display sets Warning Minimum, Warning Maximum, Display Minimum and Display Maximum for NSP's gauges.
• PC logging: Logging → Start Logging to PC (F6). Onboard logging: the Datalog page, under Add/Remove Channels.
• A Haltech dash set up in NSP can show it, and alarm on it under Functions → Alarms.

05Optional: diagnostics and cylinder shutdown

NSP can flag a high EGT and cut a cylinder that runs too hot.

1. Under Diagnostics, leave Raw Min and Raw Max off. The EGX reads close to 0 V when cold, and an open probe reads at the top of the range, the same as a real overheat, so neither voltage limit helps.
2. Operating Max flags a temperature above a limit, with its own DTC.
3. With one EGT per cylinder, Cylinder Shutdown can cut a cylinder above Max EGT after a Delay. The cut lasts until a reset or power cycle. An open probe reads hot, so it can cut its cylinder too.

06If something's wrong

It reads too high with the probe connected

Pull Up is still enabled, which skews the reading. Set Pull Up to Disable on the Wiring page.

It's wrong at every temperature

The example calibration is still loaded. Replace it with 0.000 V = 0 °C and your model's full-scale point.

It reads near full scale on a cold engine

The probe is unplugged or open. Both modules drive their output high when the probe circuit is open, so an open probe reads hot, not cold.

The reading jumps with revs, fans or the alternator

You have a grounded probe, or the black wire is on chassis ground. Fit an ungrounded probe and use the sensor ground.

It reads high once the engine bay heats up

The module is mounted somewhere too hot, or there's copper wire between the probe and the module.