TerraTrip Rally Computer Troubleshooting

First set the calibration factor to 0100. With that factor, each pulse generated by a probe will register one count on the distance display and make it much easier to troubleshoot. You should do this test before you've mounted the probe(s) in the vehicle. To determine which unit you have - the older 202/303 units have two displays and the new 202 Plus/303 Plus have a single large display.

For the 202/303 , press CAL. The distance displays show CAL and a 4 digit number with one digit flashing. The flashing digit can be adjusted by pressing S. Press F and the next digit will flash and can be adjusted. Continue pressing S and F until you get the number that you want as the calibration number. To get out of the Calibration Mode press CAL again. The distance displays will now show distance.

For the 202 Plus/303 Plus , press CAL – either CAL 1 or CAL 2 is displayed in the lower distance display. If necessary, press CAL again until the calibration number you wish to change is displayed. Then press CAL SET within 3 seconds. The number displayed will zero. Then enter the number you wish using the numbered keypad. When the number you wish is displayed, press the lower CLR and that number will be entered in the computer.

Looking at the back of the Terratrip Plug the pins are numbered as I've shown here. Pin 11 is ground and Pin 7 is +12V Battery.

Using the Speedometer Probe , the black wire goes to Pin 11, the orange wire goes to Pin 10 and the white wire goes to Pin 2 (Probe 1) or on Pin 4 (Probe 2).

Using a multimeter, measure the voltage between Pins 11 & 10 – it should measure on the order of 4 to 5 Volts. Now measure between Pins 11 and the probe input, either Pin 2 or 4. While slowly rotating the core of the speedometer probe, the voltage should vary between 0 Volts and 0.5 to 1.0 Volts. With a calibration factor of 0100, you should also get one count on the distance display. If you get those voltages, then the probe are is than likely good. If the computer is not counting, then the input to the computer is probably fried.

Using the Wheel probe , the brown wire goes to Pin 1 and the blue wire goes to Pin 2 (Probe 1) or to Pin 4 (Probe 2).

Using a multimeter, measure the voltage across pins 1 & 2 or 1 & 4 as appropriate – it should measure about 8 Volts. Touch the end of the Probe with a piece of metal and the voltage should rise by about 1.0 Volt. With a calibration factor of 0100, you should also get one count on the distance display. If you get those voltages, then the probe is more than likely good. If the computer is not counting, then the input to the computer is probably fried.