93 fuel gauge not working
Instructor
Joined: May 2009
Posts: 118
Likes: 16
From: Alexandria Kentucky
There is a fuse for the fuel pump but the sensor that drives the gauge has no fuse.
The float on the pump assembly varies a resistor between 0 ohms and 100 ohms as the tank level changes. 0 ohms indicates empty and 100 indicates a full tank.
With a full tank of gas, disconnect the harness at the fuel tank and connect a digital VOM (set to measure resistance on the Rx1 scale) between terminal "B" on the connector going to the fuel tank -- the purple wire -- and ground. It should measure 100 ohms.
If the sensor reads 0 ohms with a full tank, the purple wire going to the sensor is sorted to ground between the connector and the sensor on the assembly.
If it measures 100 ohms, connect a 100 ohm resistor between terminal "B" on the other side of the harness (the side going towards the front of the car) and ground. Turn the ignition to run and check the fuel gauge. It should read full. Replace the 100 ohm resistor with a 50 ohm resistor and the gauge should read half full. Short terminal "B" to ground and it should read empty. If it doesn't respond as stated, the problem is either in the connector at the fuel tank, the wiring between that connector and the CCM, the CCM itself or the cluster. If this is the case, you'll have to methodically check the wiring all along the path to make sure that you can measure the resistance all the way to the CCM. If it is OK all the way to the CCM, you've narrowed it down to the CCM or the cluster because the CCM takes the resistance from the sensor, encodes it and sends it within a larger data stream to the cluster. Without specialized test gear, you won't be able to narrow it down any further.
Most likely though, the purple wire going from the connector to the tank sensor is shorted to ground in which case you either have to take the assembly out and find and fix the short or you have to replace the pump assembly again.
The float on the pump assembly varies a resistor between 0 ohms and 100 ohms as the tank level changes. 0 ohms indicates empty and 100 indicates a full tank.
With a full tank of gas, disconnect the harness at the fuel tank and connect a digital VOM (set to measure resistance on the Rx1 scale) between terminal "B" on the connector going to the fuel tank -- the purple wire -- and ground. It should measure 100 ohms.
If the sensor reads 0 ohms with a full tank, the purple wire going to the sensor is sorted to ground between the connector and the sensor on the assembly.
If it measures 100 ohms, connect a 100 ohm resistor between terminal "B" on the other side of the harness (the side going towards the front of the car) and ground. Turn the ignition to run and check the fuel gauge. It should read full. Replace the 100 ohm resistor with a 50 ohm resistor and the gauge should read half full. Short terminal "B" to ground and it should read empty. If it doesn't respond as stated, the problem is either in the connector at the fuel tank, the wiring between that connector and the CCM, the CCM itself or the cluster. If this is the case, you'll have to methodically check the wiring all along the path to make sure that you can measure the resistance all the way to the CCM. If it is OK all the way to the CCM, you've narrowed it down to the CCM or the cluster because the CCM takes the resistance from the sensor, encodes it and sends it within a larger data stream to the cluster. Without specialized test gear, you won't be able to narrow it down any further.
Most likely though, the purple wire going from the connector to the tank sensor is shorted to ground in which case you either have to take the assembly out and find and fix the short or you have to replace the pump assembly again.
Pro
Joined: Mar 2008
Posts: 579
Likes: 2
From: High Bridge New Jersey
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There is a fuse for the fuel pump but the sensor that drives the gauge has no fuse.
The float on the pump assembly varies a resistor between 0 ohms and 100 ohms as the tank level changes. 0 ohms indicates empty and 100 indicates a full tank.
With a full tank of gas, disconnect the harness at the fuel tank and connect a digital VOM (set to measure resistance on the Rx1 scale) between terminal "B" on the connector going to the fuel tank -- the purple wire -- and ground. It should measure 100 ohms.
If the sensor reads 0 ohms with a full tank, the purple wire going to the sensor is sorted to ground between the connector and the sensor on the assembly.
If it measures 100 ohms, connect a 100 ohm resistor between terminal "B" on the other side of the harness (the side going towards the front of the car) and ground. Turn the ignition to run and check the fuel gauge. It should read full. Replace the 100 ohm resistor with a 50 ohm resistor and the gauge should read half full. Short terminal "B" to ground and it should read empty. If it doesn't respond as stated, the problem is either in the connector at the fuel tank, the wiring between that connector and the CCM, the CCM itself or the cluster. If this is the case, you'll have to methodically check the wiring all along the path to make sure that you can measure the resistance all the way to the CCM. If it is OK all the way to the CCM, you've narrowed it down to the CCM or the cluster because the CCM takes the resistance from the sensor, encodes it and sends it within a larger data stream to the cluster. Without specialized test gear, you won't be able to narrow it down any further.
Most likely though, the purple wire going from the connector to the tank sensor is shorted to ground in which case you either have to take the assembly out and find and fix the short or you have to replace the pump assembly again.
The float on the pump assembly varies a resistor between 0 ohms and 100 ohms as the tank level changes. 0 ohms indicates empty and 100 indicates a full tank.
With a full tank of gas, disconnect the harness at the fuel tank and connect a digital VOM (set to measure resistance on the Rx1 scale) between terminal "B" on the connector going to the fuel tank -- the purple wire -- and ground. It should measure 100 ohms.
If the sensor reads 0 ohms with a full tank, the purple wire going to the sensor is sorted to ground between the connector and the sensor on the assembly.
If it measures 100 ohms, connect a 100 ohm resistor between terminal "B" on the other side of the harness (the side going towards the front of the car) and ground. Turn the ignition to run and check the fuel gauge. It should read full. Replace the 100 ohm resistor with a 50 ohm resistor and the gauge should read half full. Short terminal "B" to ground and it should read empty. If it doesn't respond as stated, the problem is either in the connector at the fuel tank, the wiring between that connector and the CCM, the CCM itself or the cluster. If this is the case, you'll have to methodically check the wiring all along the path to make sure that you can measure the resistance all the way to the CCM. If it is OK all the way to the CCM, you've narrowed it down to the CCM or the cluster because the CCM takes the resistance from the sensor, encodes it and sends it within a larger data stream to the cluster. Without specialized test gear, you won't be able to narrow it down any further.
Most likely though, the purple wire going from the connector to the tank sensor is shorted to ground in which case you either have to take the assembly out and find and fix the short or you have to replace the pump assembly again.
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,852
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
It's not fun that's for sure!
C4-90 is sending you in the right area! A fuel gauges that has a constant empty is a gauge with power and ground, but also has a grounded out ohms wire.
Willcox Inc.
C4-90 is sending you in the right area! A fuel gauges that has a constant empty is a gauge with power and ground, but also has a grounded out ohms wire.
Willcox Inc.
Instructor
Joined: May 2009
Posts: 118
Likes: 16
From: Alexandria Kentucky
A bad CCM is a nightmare -- tough to get out and tougher still to find a quality repair source to fix it.
Replacing the original one with another one is in many ways even more of a problem since you have to find someone with a tech scan tool and the proper modules to reset the mileage and the VAT code once you finally locate a replacement CCM that you know for sure was working when removed.
But -- I'm betting that as soon as the OP checks the sensor wire coming from the pump assembly, he's going to find a short.
Replacing the original one with another one is in many ways even more of a problem since you have to find someone with a tech scan tool and the proper modules to reset the mileage and the VAT code once you finally locate a replacement CCM that you know for sure was working when removed.
But -- I'm betting that as soon as the OP checks the sensor wire coming from the pump assembly, he's going to find a short.
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,852
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
A bad CCM is a nightmare -- tough to get out and tougher still to find a quality repair source to fix it.
Replacing the original one with another one is in many ways even more of a problem since you have to find someone with a tech scan tool and the proper modules to reset the mileage and the VAT code once you finally locate a replacement CCM that you know for sure was working when removed.
But -- I'm betting that as soon as the OP checks the sensor wire coming from the pump assembly, he's going to find a short.
Replacing the original one with another one is in many ways even more of a problem since you have to find someone with a tech scan tool and the proper modules to reset the mileage and the VAT code once you finally locate a replacement CCM that you know for sure was working when removed.
But -- I'm betting that as soon as the OP checks the sensor wire coming from the pump assembly, he's going to find a short.
Sounds like the sender wire is grounded.
