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Workaround idea for oil temp sensor, need feedback
Ok, so I've been chasing an OIL TEMP : LOW problem. I've determined it's a low voltage issue upstream of the firewall. I'm getting ~3.6v all the way from the sensor plug to the firewall.
So my workaround idea is to get a 12v to 5v converter box and splice that into the 5v side of the circuit (green/white wire). That should give the sensor the constant 5v it needs without having to rely on the voltage supplied by the IPC.
So would this work? Am I setting myself up for unintended consequences?
There is a reason that you are not getting a constant 5v and Ill bet you will find that reason in the sending unit
giving it 5 volts will run the risk of sending power somewhere it shouldn't be
As the drawing shows the oil temp sensor is connected to the cluster .
My advice is to disconnect the plug at the sensor and measure the resistance value of the sensor and compare to the table below .
You can also measure the continuity of each single wire from the connector at the sensor to the connector B8:C1 and A10 to verify any wiring problems (shortquit/open wires)
As the drawing shows the oil temp sensor is connected to the cluster .
My advice is to disconnect the plug at the sensor and measure the resistance value of the sensor and compare to the table below .
You can also measure the continuity of each single wire from the connector at the sensor to the connector B8:C1 and A10 to verify any wiring problems (shortquit/open wires)
That's where I'm at. I've traced it all the way from the sensor (new/verified good) all the way back to the firewall. No damage found, and low voltage the whole way. Next stop is A10 at the IPC, which will really tell me nothing either. At this point it's obvious that the IPC is putting out insufficient voltage, hence why I want to supplement it.
It's just standard shitty late 90s GM electronics.
Is the provided schematic the one you are using to troubleshoot your issue? Where do you see that it's is a 5v supply. Are you reading the open circuit voltage or with the sensor in the circuit? Sometimes these types of circuits are configured in a way that the resistance of the sensor completes a bridge circuit and the voltage is read off the bridge. So if you are reading 3.6 volts it might be proper. High resistance in the wiring would give you low oil temp so you should check the continuity all the way back to the ipc.
Ok, so I've been chasing an OIL TEMP : LOW problem. I've determined it's a low voltage issue upstream of the firewall. I'm getting ~3.6v all the way from the sensor plug to the firewall.
So my workaround idea is to get a 12v to 5v converter box and splice that into the 5v side of the circuit (green/white wire). That should give the sensor the constant 5v it needs without having to rely on the voltage supplied by the IPC.
So would this work? Am I setting myself up for unintended consequences?
That will not work and could possibly cause harm to the ECM. The 5V reference is generated inside the ECM and is monitored by the analog to digital convertor. The ADC takes the analog (continuous voltage signal) and converts it to the digital one that the system uses. You should not attempt to add power to a powered circuit to try to compensate for a voltage loss in the system.
In essence you will be back-feeding the ECU and instead of seeing the voltage vary as it should when the sensor acts on it, it will always see 5V and error out that way - an open/high equivalent.
Last edited by Ed Ramberger; Feb 8, 2021 at 10:14 PM.
That will not work and could possibly cause harm to the ECM. The 5V reference is generated inside the ECM and is monitored by the analog to digital convertor. The ADC takes the analog (continuous voltage signal) and converts it to the digital one that the system uses. You should not attempt to add power to a powered circuit to try to compensate for a voltage loss in the system.
In essence you will be back-feeding the ECU and instead of seeing the voltage vary as it should when the sensor acts on it, it will always see 5V and error out that way - an open/high equivalent.
What if I isolated the power side of the circuit? I bought a short extension harness with the intent of splicing in the 5v line. If I completely disconnected the car's voltage input I wouldn't be back-feeding voltage to the system.
Easiest way I can explain it is it's like the ECM is doing a voltage drop test based off of the signal it sends out. I am attaching a picture from a PPT I put together to explain the concept to techs. To simplify it, the circled V represents the voltage the ADC sees as the sensor resistance changes based on temp. You can't just eliminate that part of the circuit and add your own 5V substitute. That all happens inside the ECU and is connected to the 5V reference.
Last edited by Ed Ramberger; Feb 8, 2021 at 11:05 PM.
Easiest way I can explain it is it's like the ECM is doing a voltage drop test based off of the signal it sends out. I am attaching a picture from a PPT I put together to explain the concept to techs. To simplify it, the circled V represents the voltage the ADC sees as the sensor resistance changes based on temp. You can't just eliminate that part of the circuit and add your own 5V substitute. That all happens inside the ECU and is connected to the 5V reference.
Great..... So pretty much no way to fix this POS sensor.
Great..... So pretty much no way to fix this POS sensor.
Is this another electronics part that is no longer made by GM, with no aftermarket support, either? Or is the sensor still available? I must be missing something here...
Is this another electronics part that is no longer made by GM, with no aftermarket support, either? Or is the sensor still available? I must be missing something here...
You are - there was another thread on this previously. In a nutshell the OP does not have a 5V signal to his oil temp sensor and hasn't been able to figure out why. It's not a sensor issue, it's either a component or wiring issue and it is currently undiagnosed.
You are - there was another thread on this previously. In a nutshell the OP does not have a 5V signal to his oil temp sensor and hasn't been able to figure out why. It's not a sensor issue, it's either a component or wiring issue and it is currently undiagnosed.
At this point I'm fairly certain it's a component failure. Wire is verified good from sensor to firewall, and the only thing I've done behind the dash recently is replace the hazard switch.
Workaround idea for oil temp sensor, need feedback
