Series 40E Troubleshooting – Section 43.1 Signal Functions – Two Speed Axle (TSA)

For the Two Speed Axle (TSA) circuit function diagram, see Figure
“Two Speed Axle Circuit Function Diagram”

. The ECM is programmed with the high and low rear axle ratios. The ratios are used to calculate the speedometer signal, depending on which mode the switch is in. The ECM uses the high ratio unless voltage is applied to ECM pin 28, indicating the two speed selector switch is in the low range.‪

Figure 1. Two Speed Axle Circuit Function Diagram

The two speed switch applies 12 volts to the ECM at pin 28 (and to the shifter) when the switch is in the low position.‪

Section 43.1.1
Fault Detection Management

There are no ECM diagnostics for the two speed circuits.‪