2001 Oil Pressure Gauge not working

[Int3man]

HI All,
New to me truck, Has oil pressure with mechanical gauge. Doesn't have pressure on the dash gauge. Check Gauges error light lit. Laid on the Motor and changed out the Stock pressure sending unit. Connected the new one no Joy. Any idea's? I thought that Lucas only did wiring systems for British cars!!

My 2006 Hemi Megacab had an erratic Tachometer and that was a cold solder joint on the dash. Anything similar here?

Thanks in advance.
Michael

 

[Int3man]

O.K. The plot thickens. Watched a You Tube on how to test the instrument cluster and the oil Pressure Gauge in the cluster, tests good. So with a new sending unit installed, that leaves me to the wiring. Just where I didn't want to go. I see on the schematic that the Orange 5 volt reference voltage is picked up at a junction somewhere. Any one know where that might be in the loom? I'm recovering from surgery and don't think I can get both mitts in there, at the same time, at the sending unit to test for voltages.

Again Thanks in advance.
Michael

 

[DavidC]

I haven't seen much info on gauges other than they are on the ccd bus. The ECM receives the signal, converts it to pressure and sends it to the PCM then to the gauge on the bus.

Dave

 

[PBJ2500CTD]

The oil pressure is a fairly simple system, although too many "magic boxes" are involved as well as available pressure sender part numbers that function differently. The self test indicates the gauge is functional and follows system "calibrated" values. This leaves the input to be suspect.
Was the factory dash gauge working properly when you purchased the truck, or only the mechanical gauge? Are the mechanical gauge and electrical sending unit being fed via a common "T" connector? My guess is a faulty or incorrect sending unit, or a bad connection/wire. What part number did you install?
Check out posts #11 and #12 of this link for some good information: https://www.turbodieselregister.com...ssure-sending-unit-worth.257459/#post-2496393

 

[Int3man]

The oil pressure is a fairly simple system, although too many "magic boxes" are involved as well as available pressure sender part numbers that function differently. The self test indicates the gauge is functional and follows system "calibrated" values. This leaves the input to be suspect.
Was the factory dash gauge working properly when you purchased the truck, or only the mechanical gauge? Are the mechanical gauge and electrical sending unit being fed via a common "T" connector? My guess is a faulty or incorrect sending unit, or a bad connection/wire. What part number did you install?
Check out posts #11 and #12 of this link for some good information: https://www.turbodieselregister.com...ssure-sending-unit-worth.257459/#post-2496393

Nope the Dash Gauge never did work. I verified that it had pressure with a mechanical at the filter assembly, before plunking my monies down. I purchased a $30 sending unit on eBay and screwed it in, no difference. A gentleman sent me a link to Mopar 1973 man and he suggest that the MAP sensor is connected in Parallel to the 5v source for the Oil Pressure sending unit. He replaced it and his now works! So I'm waiting for a MAP Sensor to come in.

If I can get in there with a volt meter I'll verify +5VDC. Thanks for the heads up on the part numbers. If all else fails I'll try a Geno's.
Thanks Michael

 

[DavidC]

I think you can unplug the map and start the truck to see if pressure works. Not sure if it will light up the check engine. I believe that is a soft code and goes away after so many starts and/or miles without a fault.

Dave

 

[PBJ2500CTD]

I think you can unplug the map and start the truck to see if pressure works. Not sure if it will light up the check engine. I believe that is a soft code and goes away after so many starts and/or miles without a fault.

Dave

^^^ What Dave said...^^^
It's sad that so many tests require a DRB tool to trouble shoot. If we knew the resistance parameters of the oil pressure sending unit and had a variable DC power supply for the 5 VDC we could simulate an output signal. That's asking a bit much for most tool boxes. Alternately, as long as the sending unit is serviceable, the fixed resistance value can be found by checking across pins A and B of the transmitter.

The pinout below is from the 2002 service manual wiring diagram:

Pin A of the oil pressure transmitter receives 5 VDC from pin 10 of the ECM; Wire info K7 18 OR
Pin B of the oil pressure transmitter supplies the "sensor" (transmitter) ground through pin 11 of the ECM; Wire info K104 18 BK/LB
Pin C of the oil pressure transmitter sends a variable signal related to oil pressure to pin 6 of the ECM. Wire info G60 18 GY/BK

Check pin A for 5 VDC with a multimeter, with ignition switch on; If correct voltage is not observed check wiring harness continuity from pin A (transmitter) to pin 10 (ECM);
To confirm function of the transmitter you could disconnect the oil transmitter plug and take the resistance measurement with an ohmmeter between pins B and C of the transmitter with the engine off, running at idle, and running above 1,500 rpm. This should show three different resistance values for no oil pressure, idle (lower) pressure, and operational (higher) oil pressures. The tough part is getting a good connection on the pins of the transmitter.

Hope this helps...

 

[Int3man]

O.K. More Broth for the stew. Got up this morning to a light Sprinkle in Seattle. Truck is from California. So moisture is new to it. The Oil gauge worked for half the day then it went out on Strike again for the afternoon. So I think the relative humidity effected the 5 volt junction and got it to work. At least I have a starting point when I get home.

Michael

 

[KrisKringle]

Wow...what a bunch of info. It is cooling off here in Germany. Yesterday I started the truck without thinking and eliminated any surviving mosquitoes. This morning I waited for the engine light to go out (pre-heat) and noticed that the oil pressure gauge reads the same with the key on as when the engine is running. My first thought was the sender. Does anyone have the ohm readings for the sender?

 

[DavidC]

Try unplugging to make sure it is sender.

Dave