Guide · AEM Infinity

EGT on AEM Infinity

An AEM Infinity reads an exhaust gas temperature amplifier on a spare 0 – 5 V analog input. The input shows as a voltage, and an InfinityTuner virtual channel turns it into a temperature. This guide covers the pins, the wiring, the virtual channel and logging.

Checked against AEM's Infinity manual, hardware specifications and quick-start guide, September 2026. AEM Series 2 units use different software and aren't covered here.

00What you need

• An AEM Infinity ECU (Series 3, 5 or 7) with a free analog input, and InfinityTuner connected over USB. On a plug-and-play kit, find a spare input in the kit's instructions.
• An EG5 for the ECU's +5V Sensor Power, or an EG12 for switched 12 V.
• A Type K probe and a bung or O2-port adapter for it, bought to the specifications under Recommended to use with.
• A multimeter.

Electrical

01Pick an input

Infinity analog inputs read 0 – 5 V at 12-bit resolution. Each one has a 100 kΩ pull-up to 5 V, which the EG's output drives directly.

• Inputs with no default function:
  Series 5: Analog 10, 11, 16, 18 and 19 (C1-75, 74, 71, 70, 69).
  Series 3: Analog 10, 11, 16, 18 and 19 (C1-43, 46, 48, 49, 50).
  Series 7: Analog 10, 11 and 12 (C1-38, 39, 40), 14 (C2-19) and 20 (C2-33).
• Check Pin Out first, on the Setup Wizard's Input Function Assignments page. A calibration or harness can still use one of those. On drive-by-wire engines, Analog 16, 18 and 19 are often the throttle and pedal sensors.
• Avoid Analog 7 (TPS), 8 (MAP), 9 (fuel pressure) and 13 (oil pressure), and on Series 7 also 15 – 19, 21 and 23.
• Skip the Analog Temp inputs. They have 2.49 kΩ pull-ups for temperature sensors.

02Wire it

• EG12: the Infinity has no 12 V sensor pin. Use a fused, switched 12 V feed, such as the EFI main relay output. AEM says to fuse every 12 V lead you add and to keep other loads off the ignition switch wire.
• Use the sensor ground, not chassis. Every 4 – 5 mV of ground offset reads as about 1 °C.
• An EG5 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.
• Neither output can go much above 5 V. The EG5 can't rise above its own 5 V supply, and the EG12 is capped at about 5.3 V.

Probe side

• The thermocouple cable is cut square. Take the jacket back, strip the yellow and red, and splice yellow to the probe's + and red to −. The cable is Type K extension, so the splice can sit anywhere along its run.
• Check the polarity. A reversed probe reads right at room temperature, so once it is spliced, warm the probe's tip: the reading must rise. If it falls, swap the probe's two leads at the splices. On a probe whose leads are not marked, the − lead is the one a magnet sticks to.
• 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 EG5, under 100 °C for an EG12.

Software

03Set it up in InfinityTuner

Leave the input unassigned, and build the temperature in a virtual channel.

1. With the ECU powered and connected, open the Setup Wizard, go to Input Function Assignments and click Pin Out to confirm nothing uses your input.
2. Find the live channel for your input, such as Analog10 [V]. With the probe connected at room temperature, it should read a little above 0 V.
3. Open Layout → Add virtual channel. Give it a Name: such as EGT, use Set Inputs to make your Analog channel input i0, and enter the Expression:
   EG5: i0 * 200 for °C, or i0 * 360 + 32 for °F.
   EG12: i0 * 250 for °C, or i0 * 450 + 32 for °F.
4. Save your session and layout so InfinityTuner keeps the virtual channel. ECU changes are saved when you close the Setup Wizard, or with ECU → Commit modifications.

The multipliers come from the calibration points above: the full-scale temperature divided by the full-scale voltage.

A dash means past that model's range.

04See it and log it

• Layout → Add Control → Gauge, then right-click it and Set Channel to your virtual channel.
• PC log: Logging → Start PC Logging, then Stop and Save PC Log, then File → Save session to keep it.
• ECU log (Series 5 and 7 only; Series 3 has no USB logging): Logging → USB Logging - Channel Setup, while connected. Log the Analog input's voltage, and convert it with the same multiplier. A firmware update clears this channel list.
• Treat this as a gauge and a log, not engine protection.

Troubleshooting

It reads near full scale and won't move

A disconnected signal wire. Infinity inputs have a 100 kΩ pull-up to 5 V, so an open wire reads near full scale, like a disconnected probe.

The virtual channel shows nothing

Check that Set Inputs points i0 at the Analog channel you wired, and that the channel shows a voltage.

It reads near full scale on a cold engine

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

The reading falls as the exhaust heats up

The probe's leads are reversed at the splices. A reversed probe reads right at room temperature, then falls toward 0 °C as its tip heats. Swap the probe's two leads.

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.