97XJ 4.0 Sport odometer error.

XJ purchased 8 months ago, shows 228,000. Extremely clean, looks, drives like new.

Noticed the odometer jump up 600 miles while driving it. Today, topped the fuel off, used 7 gallon, odometer showed 315 miles since the last fill up. Actual miles driven was 105. I know that the trip meter was reset, am sure this odometer / trip meter is intermittent and adding miles every so often. Spot checks with the gps, shows the speedo is correct.

I could live with the odometer error, except that I want to change oil at 3,000 miles, & I can't trust the odometer.

Any suggestions or troubleshooting tips would be appreciated. Thanks

Buy used gauges and see if the problem continues

On the 97, the transfer case (transmission for the 2WD) turns a gear that spins a transmitter (VSS) that in turn sends a square wave signal to the PCM where a frequency counter converts the signal to something useful. The PCM then sends that information on the Bus to the cluster and the cluster decodes and displays that data along with all of the other gauge data.

For the odometer to be off and not the speedometer is odd to say the least. As I recall, the mileage is recorded on the electronics in the cluster itself, not the PCM.

Certainly swapping out the cluster is a good first step. Make sure you note the total mileage on the Heep when you make the swap. Some States, as a Consumer Protection, require documentation on odometer replacements.

If the VSS were bad, it should be throwing CELs. With my Heep, I had to alter the frequency to get the thing accurate as I am running P285/75 tires and 4.56 gears with the AW4. Net change to the signal is a -10.9% to get the speedo/odo accurate. No Huhu.

O-Gauge Steamer said:

For the odometer to be off and not the speedometer is odd to say the least. As I recall, the mileage is recorded on the electronics in the cluster itself, not the PCM.

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The mileage is stored on the PCM and gauge cluster. The PCM reads the speed sensor then relays essentially a +1 to the gauge cluster. The gauge cluster can have a different mileage stored than the PCM and still increment correctly.

If IC13, the 93c56 EEPROM, on the gauge cluster circuit board has bad memory locations then it will begin to cause funky counting that you are seeing since it uses a ring array for counting.