2.3L ('83-'97) Engine sensors

[Redleg68]

Does anyone have a diagram of the sensors and location?
Trying to find out what the sensor located on the back of the head is and the one below the back cylinder intake are.
Thanks

 

[Shran]

I believe the top one is the oil pressure sending unit and the bottom is the coolant temp sending unit. I haven't touched those in like 8 years on my trucks so I might be mistaken.

 

[RonD]

+1 ^^^

Seen here: https://cimg4.ibsrv.net/gimg/www.ra..._d3c13ce3af4920cf917bb86d6913e996a27c731c.gif

Not "sensors", they are both 12volt Senders, used for dash board temp and oil gauges
"Sensors" are 5volt and only used, connected to, the engine computer

 

[Redleg68]

+1 ^^^

Seen here: https://cimg4.ibsrv.net/gimg/www.ra..._d3c13ce3af4920cf917bb86d6913e996a27c731c.gif

Not "sensors", they are both 12volt Senders, used for dash board temp and oil gauges
"Sensors" are 5volt and only used, connected to, the engine computer

So the one on the heater core hose line I assume just talks to the computer? Along with the sensor towards the front of the motor?

 

[RonD]

Yes, on some years the 2.3l has the ECT(engine coolant temp) sensor on a heater hose
Sensors are always at least 2 wires, some are 3 or 4 wires

ECT sensor is important, it sets "choke" mode on cold starts and allows computer to go into Closed Loop mode once coolant is above 150degF

Other sensors are
TPS(throttle position sensor), 3 wire, on the throttle plate shaft
MAF sensor, 4 wire, on air intake tube, 2 wires are for 12volt heater
IAT(intake air temp) sensor, 2 wire, can also be called ACT sensor, can be on upper intake or on air filter box
Knock sensor, 2 wire, only used in some years on some model engines, usually mounted on passenger side block

O2 sensor, 4 wire, 2 wires are for 12v heater, these are different, they generate their own voltage, 0.1v to 0.9v, also the ONLY sensors that wear out, 12 years or 100k miles and they start to run out of the chemical that generates the voltage
So change these on time or miles, or if you are unsure when they were last changed
On a pre-1995 4cyl you would only have 1 O2 sensor

Engines also have Controls
IAC(idle air control) Valve, 2 wire, 12volts, computer uses it to set idle RPMs, can/should be cleaned every now and then
EGR(exhaust gas recirculation) system, 2 wire, 12volt solenoid, only used when engine is warmed up, and only when engine load is higher, prevents high NOX emissions(toxic gas) also helps prevent pinging/knocking

 

[Redleg68]

Thanks!! VERY helpful, appreciate the info