CAT Engine 7742 Fault Code: Secondary Throttle Position Sensor: Erratic, Intermittent, or Incorrect

What does CAT Engine error code 7742 mean?

This code covers the secondary (throttle #2) input, whether that is a multi-position rotary throttle switch or a second throttle position sensor mounted on a pedal assembly. The ECM expects a specific, defined pattern from that input. When it sees a combination of switch positions that does not match any valid position, or an erratic/intermittent signal, it flags code 7742.

On machines equipped with two throttles, the ECM will simply keep using the working (primary) throttle until the fault is repaired, so the operator may not notice much change. On machines with only one throttle, or where the second throttle itself has failed, the engine defaults to a limp home speed. If the engine was running faster than that speed, it decelerates down to it. If it was running slower, it stays where it is. Either way, the engine is stuck at that speed as long as the code stays active.

Once the code sets, the ECM ignores all input from the faulty throttle, and even after the wiring or switch is repaired, it will continue ignoring that input until the keyswitch is cycled off and back on. The throttle position sensor itself is a PWM device mounted on the pedal assembly and cannot be adjusted: 0 percent duty cycle corresponds to pedal released, 100 percent to pedal fully depressed.

What triggers a CAT Engine 7742 code?

The ECM sets this code when it detects a throttle switch position pattern that does not match any of the defined valid positions, or when the secondary throttle signal is erratic or intermittent. For multi-position switch circuits, normal voltage at the throttle inputs to the ECM should read 13.8 VDC (plus or minus 0.5 VDC) when the throttle inputs are open, and less than 0.5 VDC when the throttle inputs are closed; a pattern outside these expected states triggers the fault.

Common causes of 7742

• Damaged connectors or wiring at the throttle switch or sensor circuit
• General problem with the wiring harness
• Intermittent connection or wiring fault
• Faulty throttle switch (multi-position rotary type)
• Faulty secondary throttle position sensor
• Faulty ECM (listed for the switch-position variant of this code)
• Incorrect ECM software configuration for a multi-position throttle setup

How to troubleshoot CAT Engine 7742: first checks

1. 1Verify the ECM software configuration is correct for a multi-position throttle setup before chasing wiring.
2. 2Inspect all connectors and wiring on the secondary throttle switch or sensor circuit for corrosion, damage, or loose pins.
3. 3With the key on and throttle inputs open, check voltage at the ECM throttle inputs; it should read close to 13.8 VDC (± 0.5 VDC). Check that it drops below 0.5 VDC when the inputs are closed.
4. 4Cycle through each switch position (if a rotary multi-position switch) and confirm each produces a valid, repeatable ON/OFF pattern, watching for intermittent dropout.
5. 5If a second throttle sensor is installed, check that its PWM output moves smoothly between minimum duty cycle (pedal released, 0 percent) and maximum duty cycle (pedal fully depressed, 100 percent) with no dead spots or erratic jumps.
6. 6Inspect the pedal assembly geometry for wear or damage, since the sensor cannot be adjusted and depends on the pedal's mechanical travel.

How the code clears

Repairing the wiring, connector, switch, or sensor does not clear the fault by itself. All inputs from the repaired throttle continue to be ignored by the ECM until the keyswitch is turned off and back on. No separate reset procedure beyond the key cycle is listed for this code.

Affected models and serial ranges

7742 appears in our records across 3 CAT Engine models. Match your machine by model and serial number.