Whoa! Makes you long for the days of a simple mechanical guage, huh?

Bob

 

so based on reading that master tech, i take it you are thinking the cluster is the problem?? even tho it passed its self check??

 

so i unplugged the sensor and if i turn the truck on (did NOT start it) the oil pressure gauge comes up to the red line and sits there, (it doesnt move much and iv you dont watch it you really cant tell)

i also did some more reading in the factory service manual and because when engine speed is at 0 the oil pressure guage should be all the way to L i went ahead and unplugged the crank position sensor (the pcm uses this to calculate engine speed), the guage still behaves the same way.

after taking these steps im about 90% sure that i need a new pressure sensor.

master tech, do you agree or disagree??

sensor disconnected


ignition in off/lock position




edit: pulled the sensor and i get 137k ohms between the sensor pin and the signal power line with the sensor sitting on the bench (0psi) that seems odd to me, but has anyone else checked theirs to know?

 

I would agree with the sensor. Its very rare to see a problem with a gauge or cluster.

 

ok i will see what i can do about getting it changed before i go back to school (i move in on friday) if its not done by then it will be done at my fathers convience since he works full time and the truck isnt driven much when im not home, thanks for your input.

 

OPERATION
The oil pressure sensor uses two circuits. They are:
. A signal to the PCM relating to engine oil pressure
. A sensor ground through the PCM’s sensor
return
The oil pressure sensor returns a voltage signal
back to the PCM relating to engine oil pressure. This
signal is then transferred (bussed) to the instrument
panel on a CCD bus circuit to operate the oil pressure
gauge and the check gauges lamp. Ground for
the sensor is provided by the PCM through a lownoise
sensor return.

I couldn't find the resistance values but that does sound low. I checked in my Chiltons page 2-16 book version 20404 and it has instructions.

It says to disconnect the sensor and the ground side return to ground. Turn on the key and low pressure light should go on. Disconnect jumper and the light should go off. If the lamp does NOT light suspect a burned bulb or wiring issue.

Also:
With engine off and gauge at "0" check for continuity across the switch leads. There should be continuity. If not replace the switch.

 

you dont take the truck up to school with you?

 

srch, no i dont take my truck to school because i go to school in the city, and parking is rough on cars to begin with, and in order to get a spot it would cost me $100 a MONTH!!!!!!!!! so i leave it at home where i am only an hour train ride away and i have the truck (a $9 train ride on the very rare occasion that i need it is much easier on the wallet)


now for the sensor ohm reading

locking mechanism on the plug up

|+-+|
|123|
|___|

i believe that pin 1 in this rough diagram is the input voltage

pins 1-2 = 134.4 kohms
pins 1-3 = 109.2 kohms
pins 2-3 = 244 kohms

since none of these are the closed (0 ohms, continuity) that hydras little excerpt calls for im on my way out to the store now

 

ok so new sensor, same diagram

pins 1-2 = open
pins 1-3 = 10.9 kohm
pins 2-3 = open

however it still reads pressure with the key on and the engine off

 

ok guys last update since i resolved the issue, it ended up being a combination of 2 things,

1) a bad oil pressure sending unit (oil pressure sensor)
2) dirt/water/ect lodged into the connector,

this afternoon i put the D in the garage and took the plug apart and blew it out from both sides using compressed air and now it is working fine (only with the new sensor).


now for the full story in case anybody wants it (if you have ADD or ADHD and skip this its fine )

i started out after the new sensor didnt fix it by pulling out the connector pin outs and checking for continuity between the PCM and the pressure sensor (all 3 leads came back good, sorry i didnt write down which ones were which, but the FSM has all the information you need), so then i put our OBDII tool on the truck and hit the erase button (it did NOT show any codes, but i did it anyway). now i know that i have good connections everywhere i took plug back off the sensor and starting blowing it out with compressed air from the end where the sensor plugs in. no dice. so i took the back off, and pried the sealing material out of the back and blew it out with compressed air (our compressor puts out about 120-130 PSI) plugged the sensor back in and everything worked, started the truck up, pressure gave me a reading as designed, turned it off and back on, and it went back down, problem solved.

the big hint that it was the connector in all of this was that there was a 'sweet spot' on the plug being pushed onto the sensor where it would work correctly, but it was such a finicky spot that the plug wouldnt have stayed on if it had just been left, something had to be removed from the plug to make it work correctly, what was stuck in there, i have NO CLUE, but its gone and the problem is solved, maybe this will help someone else at some point now that i have done the hard part (you know the diagnosis and solving, now they just have to repeat it!!!)

ok off to drink some beer and celebrate