Check Road Speed Signal

NOTE: Test Mode 2. Once test mode 2 is activated, the ECC control module cannot control the cabin climate.

The road speed signal is a square wave which varies in proportion with the speed of the car. The input signal comes from the speedometer output on the combined instrument panel. If the signal is wrong or absent, the control module will not receive the right information.

To Check The Road Speed Signal:





WARNING: Chock rear wheels and set emergency brake.

- Jack car up so wheels can turn freely. The equivalent road speed needs to be at least 10 km/h (5 mph) before the control module can detect the signal.
- Start test mode 2. Initializing Test Modes
- Control module should respond to road speed signal with acknowledgement code 1-1-3. The control module will continue to flash the acknowledgement code even once test mode 2 is activated. If the solar sensor is activated at the same time, the solar sensor acknowledgement code will appear first (1-1-2) followed by the road speed signal acknowledgement code (1-1-3); the control module will continue to flash these codes until the ignition is switched off.





- If test mode 1-1-3 does not appear, LED flashes rapidly but no acknowledgement code appears:
- Ignition off.
- Cover solar sensor.
- Ignition on.
- Start test mode 2.
- Let car wheels rum freely.
- Open throttle.
- If no acknowledgement code appears after a number of attempts, there may be a problem with the road speed signal impulse sensor in the ignition system, the combined instrument panel or wires.
Go to next step "Check Speedometer".

Check Speedometer:
Check if speedometer is working.
- If the speedometer is working, this means a road speed signal is reaching the combined instrument panel. This means there may be an open circuit in the wire from the combined instrument panel or in the combined instrument panel output. Go to step "Connecting Test Unit To Control Unit".
- If the speedometer is not working, this means no road speed signal is reaching the combined instrument panel. This may indicate a fault in the road speed signal impulse sensor, ignition system, combined instrument panel or wires to the combined instrument panel. For more information refer to "Powertrain Management".

Connecting Test Unit To Control Unit:





- Ignition off.
- Connect test unit between control unit and air-conditioning system connector as shown in "Connecting and Disconnecting Test Unit" and check ground (GND) points. Connecting and Disconnecting Test Unit
- Go to next step "Check Road Speed Signal".

Check Road Speed Signal:








WARNING: Chock rear wheels and set parking brake.

- Jack car up so wheels can turn freely.
- Ignition on.
- Connect voltmeter across # 10 (0 V) and # 24.
- Spin front wheels.
- If value is OK, voltmeter should fluctuate between 0 V and 12 V.
- If voltmeter reading is constant. If the voltmeter shows a constant low (0 V) or high (battery) voltage, there is an open circuit or short in the wire.
Check wire between combined instrument panel output A:6 and connector A pin A:24 to control module for short or open circuit as in "Checking Wires". Checking Wires
Correct fault.
Go above to the step "Start test mode 2".