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sprinkles08, Chrysler/Dodge/Jeep master tech
Category: Dodge
Satisfied Customers: 21434
Experience:  ASE Master and Advanced Certified, Chrysler/Dodge/Jeep Master Certified, Trans and Hybrid Specialist
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Dodge Ram 1500: we have a 2003 R-1500 with 3.7 liter and it

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we have a 2003 R-1500 with 3.7 liter and it isXXXXXand we did a trany and a heater core the truck runs great just that the oil gauge sits at low and if you drive it then it will go all over the place we have replaced the op sender checked all the grounds in the engine compartment and also on the ecm and also we had done oil pressure test and at idle it was 70 psi and at 3000 rpm it was 90

Hello and welcome to JustAnswer!


Does the problem with the gauge only happen when the engine is hot or is it all the time? If it only happens when the engine is hot then you'll also need to check oil pressure with the gauge when the engine is hot and it would normally be acting up. With the pressures that you saw it's clear that the engine wasn't up to operating temperature, which is when you would expect more problems with actual oil pressure.


If the symptoms are identical then we should be able to rule the sender out. That would leave only a problem with it's wiring between the sender and powertrain control module (PCM), the PCM itself which isn't very likely, or it could be the instrument cluster.


If oil pressure can be verified as ok when the engine is hot then the next thing I would do is use a scan tool to see what the PCM is seeing for oil pressure. It's a switch rather than a sensor so you'll see it in one of two states, either pressure or no pressure. If you see pressure coming and going on a scan tool then you know it's a sender, wiring or oil pressure issue. If the PCM is seeing pressure even when the gauge drops out then it's going to be a cluster issue.

Customer: replied 3 years ago.

when we had looked at the scanner it had said the volts where at 4.98 and could not get it to go to zero and it was running at this time as far as the pressure I would have to look at it tomarrow when get to work

If it was at 4.98v that was with the gauge at 0, correct? When oil pressure goes above 6 PSI then the switch should close and ground the wire which takes the reference voltage to 0, the gauge comes up to the half way point.
Customer: replied 3 years ago.

is there any way to check because when we look at the scanner and when the gauge goes up the volt seem to stay the same but it goes so fast that I don't think the scanner can catch it but if ok with you have to catch some zzzzzzzzs will talk to you tomarrow but if there is any thing you want me to check in the am put it down and I will reply it back to you

If it drops and comes back quickly the scan tool may not be able to pick that up, they often don't refresh quickly enough to see things like that. If you have a labscope you can set it up to monitor the circuit and may be able to see it drop or you may be able to data record the voltage if you have that capability.

If the voltage doesn't look like it's dropping on the scan tool you can at least try to monitor it with a voltmeter if you don't have a labscope. Like a scan tool a voltmeter may not be able to catch a drop if it happens fast enough but you might be able to see something.

I'm a full time tech and will be at work tomorrow but I do get to check in here regularly. If you post back while I am offline I'll get back to you as quickly as I can.
Customer: replied 3 years ago.

Ok I did look at the scanner and it said for oil pressure volts was 4.98 and the pressure was 0.0 and I also did a Actuator test and all of the gauges and lights had worked on the instrument cluster when I go down to the oil sender wire and used the power prob all it shows is ground. and I also checked the wire from the oil pressure switch and it was good witch was gray and yellow wire and I have been reading and it says that this should be a 3 wire connector but it is only 1 wire and that also shows 1 wire on wiring diag to

The sender is a single wire, it's a switch rather than a sensor.


Using a digital voltmeter, sender unplugged and key turned on what voltage do you see at the sender connector?

Customer: replied 3 years ago.

0.00 Volts at the connector and at the sender 0.00 volts to

If you have 0 at the sender connector but the scan tool is showing 5v then either the wire is broken or the problem is internal in the PCM.

If you measure resistance of the wire between the connector and pin 23 if the center PCM connector (the same gray/yellow wire) what resistance do you see?

Customer: replied 3 years ago.

I did do that and it showed 0 when checking resistance

Is it 0 or 0L? If it's 0 ohms, the same as if you touched the test leads together, then the problem has to be in the PCM.

If it's 0L, the meter display doesn't change when probing the wires, then the circuit is open.
Customer: replied 3 years ago.

ok sorry on my meter it starts with 1 and when you touch them together it goes to 0 so I would say then the problem is in the pcm would you agree

Yes. If the PCM is seeing 5v on the circuit but it is actually 0 and the wire is good then it has to be the PCM. There's an internal open circuit before it leaves the PCM.
Customer: replied 3 years ago.

Ok thank you so much for your time that should get the boss off my but now to try to fig out how to tell the cu that they need to replace the pcm and get reflashed

You're welcome and good luck with it!
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