Hi Bonzo,

Bendix Regina (Fuel Injection) is a code presented using the OBD-1 socket 2 test unit



https://www.brickboard.com/FAQ/700-900/EngineOBDCodes.htm

So, on the FAQ Web Page: Table 3: Regina Fuel Injection Fault Codes.

"1-2-2: Signal missing or faulty to/from air temperature sensor Air temperature sensor"

The Rex ignition control has no corresponding fault code as it does not use the

Image of Intake Air Temperature Sensor:


Another view:


Another view:


The fault code may condemn a fault in the wire harness between the air temperature sensor and the Regina ECU controller. Wire line corrosion at any connector?

At any rate, this PDF file shows the location of the Regina air temp sensor (copy asd paste):
https://www.matthewsvolvosite.com/forums/download/file.php?id=8581

The air temperature sensor is:

FCP Euro Gebuine Volvo) 54$:
https://www.fcpeuro.com/products/volvo-air-temperature-sensor-models-with-regina-1389556

Tasca Volvo Parts 47$
https://www.tascaparts.com/oem-parts/volvo-volvo-intake-air-temperature-iat-sensor-1389556

iPd (outa stock - appears OEM) 32$:
https://www.ipdusa.com/products/9281/120676-intake-air-temp-iat-sensor-740-940-rex-regina

https://www.brickboard.com/FAQ/700-900/EngineSensors.htm#ReginaAirTemperatureSensor

I dunno who makes this part. I'll guess Bendix. Bendix Regina (fuel - OBD socket 2) has an error code specific to this sensor, so replacing sensors where the ECUs do not report a corresponding fault may not solve your symptoms.

Also, in your Regina air filter air box, upstream (dirty air side) of the air filter is a preheater control flappy valve controlled by an air thermostat made by Wahler (Whaler?). These will fail to all hot all the time, and may cause the air temp sensor to fail or misread ambient air temp conditions so the Bendix engine control in your 1991 Volvo 740 operates well no matter the air induction intake piping temp.

So, as your local and state emissions control allow, you can:
- Replace the air temp sensor controlling the preheat flap valve
- Remove the silver accordion hose between the air filter box and the exhaust manifold heat shield, and then remove the assembly from your air box.

So, some example air temp preheat controller thermostats made by (Borg-Warner) Whaler (PN 70411)





Tasca Auto Parts - 49$:
https://www.tascaparts.com/oem-parts/volvo-thermostat-1266826
(May be made in Europa at that price?)

iPd 13$:
https://www.ipdusa.com/products/5451/103083-airbox-thermostat-valve

FCP Euro - 10$
https://www.fcpeuro.com/products/volvo-engine-air-box-thermostat-1266826

Though I expect with more 700-900 ownership expereince like Spook can provide more insight into Bendix Rex / Regina foibles.

Hope that helps.

Questions?

Gigafactory Hopeful MacDuffed.
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