Hi LKM,
Swoop223 has giving directon of how to test the sensor and yes the temp at the maifold will be much higher as that is where the combusion gases exit. LP trucks do have higher temps than regular Diesels. The Engine Oil Pressure sensor is there as a safety device to stop the engine, if it thinks there is risk of damage, so it is either reading something being wrong or it is not working correctly.
Note that Combilift have tech support beside you in North Carolina in Greensboro along with a Parts Hub. If you complete the "Technical support" form at the bottom of the www.Combilift.com web site, then one of the team will be in contact with you.
Hope you get sorted.
Thanks,
Richard
if your taking your block temp reading near the exhaust manifold of course it will read that high. I would say that is normal.
First look at the oil pressure sensor and make sure it is not leaking.
Then remove it and attach an oil pressure guage and get a physical reading to make sure it actually has pressure. I'm sure when cold the pressure will be high, around 50 or 60 psi maybe, then as it warms up it will drop to about half of that probably. It all depends on the condition of the oil and the weight used.
If you think the oil is breaking down then change it and the filter.
If the pressure checks out ok then replace the sensor.