have installed an ECUMaster PMU16 in my Toyota MR2 SW20 and I am currently using two analog inputs for temperature sensors. Both sensors are Toyota OEM-style 2-wire temperature sensors, but I am getting abnormal readings from both of them.
Vehicle / Device
- Vehicle: Toyota MR2 SW20
- Device: ECUMaster PMU16
- Sensor type: Toyota OEM-style 2-wire temperature sensors
- Sensor supply used: PMU16 +5V output
- Sensor setup in PMU Client: calibrated analog temperature sensor
Sensor 1: Engine bay temperature sensor
- Sensor: Toyota OEM temperature sensor, part number 89424-87703
- Location: Engine bay
- Pull-up resistor: 4.7kΩ from PMU16 +5V to the signal wire
- Signal wire: Connected to PMU16 analog input
- Sensor ground: Connected to chassis ground
Issue:
When I first power/start the car, this sensor reads 65535°C. After the engine has been running for a while, the reading becomes normal and appears to read correctly.
Sensor 2: Front ambient temperature sensor
- Sensor: Toyota OEM ambient temperature sensor
- Location: Behind the front bumper / front airflow area
- Pull-up resistor: 1kΩ from PMU16 +5V to the signal wire
- Signal wire: Connected to PMU16 analog input
- Sensor ground: Connected to the engine valve cover
Issue:
This sensor reads normally when everything is cold, around 35°C. However, after a few minutes after starting the engine, the reading suddenly goes very high, around 288°C. When I checked the analog voltage reading in PMU Client, the voltage had dropped to 0V.
PMU Client input setup
For both sensors, I am using:
- Type: calibrated analog sensor
- Quantity/unit: Temperature / °C
- Pull-up / pull-down setting: default 1M pulldown
- External pull-up resistor used from PMU16 +5V to signal wire
I would appreciate advice on what could cause these readings and whether my wiring, grounding, pull-up arrangement, or PMU Client setup should be changed.
Thank you.
