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How can we test to be sure that the sender is actually sending voltage? I searched but didn't see any threads addressing this question.
Using a volt meter with the engine running, I put one diode on the tip of the unit where the wire attaches, and the other on the engine block. I didn't get a reading. Should I get a reading by doing this?
You said "oil pressure sender", so I assume you have an oil pressure gauge.
The oil pressure sender is a actually variable resistor (also called a rheostat or potentiometer) It's resistance changes as the oil pressure changes. Unfortunately you can't measure the resistance of it with an ohmmeter, when the engine isn't running the sender is almost a perfect insulator (infinity resistance) You won't get a reading on your meter. If it's digital it will just display overload!
Here's how Toyota says to test it!
Disconnect the lead from the sender. Run a 12v. lead from the pos. post of your battery. Connect a 3.4 watt 12v. bulb in series with this lead then connect the other side of the bulb to the sender. (Toyota cluster bulbs are typically 11W. and 27W. so you will have to source a 3.4w. bulb elsewhere). Check that the bulb does not light with the engine stopped and flashes with the engine running. The number of flashes should vary with engine speed. If operation is not correct replace the sender.
To check the gauge in the dash, you need an analog dc voltmeter, you remove the lead off of the sender and connect the pos. lead of the voltmeter to it. Then you take the neg. lead of the voltmeter to ground. Turn the ignition switch to the on position and the voltmeter needle should vibrate around the 4.5 volt position. The resistance of the gauge in the dash is approx. 44 ohms.
This of course assumes that your wiring from the sender to the gauge is intact, which if you are having oil pressure problems might not be!
I've never had to replace an oil sender, but I've had the wire from the oil pressure sender break on two of my Toyotas and this may be your problem. It breaks about 6 inches up in the harness from the sender on the 22re's, I can't speak on the 3.0's or the 3.4's, but it's worth a check. This must be a problem with Toyotas, because when I did my 5m-ge conversion in my pickup, there was a piece of plastic supporting the sender wire from the sender up about 8-10 inches in the 5M-ge harness. Easiest way to check this is take the connector off of the back of your cluster and check continuity (ohmmeter with a reading of little or no resistance)from there to the sender. I don't know what your truck is but my 86 and 89 runners used a Yellow/black wire and you should find it in the connector closest to the oil gauge in your dash, if you are not sure just follow the ground tracer in the printed circuit from the gauge back to the connector.
Hopes this helps.
Good Luck!
Well, it is 2019 and this feed is 14 years old. Lets see if anyone is still around.
I bought my '90 truck off the show room floor in Alamogordo, NM July 1990. My 1990 toyota pickup SR5 ext cab 4wd 22re oil pressure gauge went bad. The gauge was working but then stopped working when I was on the road. I watched the gauge sputter and then finally go to the lowest or no reading. While I had the dash cluster apart for a speedo cable replacement, I decided to tackle this oil pressure gauge.
I replaced/spliced a new piece of wire 10 inches up from the sender connector. I put a ohm meter to the back two leads of the oil gauge while the truck was running and am getting variable readings as I believe it should because of variable oil pressure at any time. I am pretty sure the problem is the gauge.
Does anyone know why this gauge is not working? What inside the gauge could be bad. Pictures of the gauge below.
06-30-2009, 02:01 AM
SR5 Oil Pressure Sending Unit Test
(on llamas)
