Internal Mode Switch ‘S’ Circuit Low Voltage
Table of contents
P1840 CHEVROLET Possible Causes
- Faulty Internal Mode Switch
- Internal Mode Switch harness is open or shorted
- Internal Mode Switch circuit poor electrical connection
How do I fix code P1840 CHEVROLET?
Check the “Possible Causes” listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector’s pins.
Cost of diagnosing the P1840 CHEVROLET code
The cost of diagnosing the P1840 CHEVROLET code is 1.0 hour of labor. The auto repair labor rates vary by location, your vehicle’s make and model, and even your engine type. Most auto repairs shops charge between $75 and $150 per hour.
Possible Symptoms
- Engine Light ON (or Service Engine Soon Warning Light)
P1840 CHEVROLET Description
The internal mode switch indicates to the Transmission Control Module (TCM) which gear position the vehicle operator has selected. The internal mode switch consists of 5 separate hall effect switches. Each hall effect switch is supplied a 9 V reference circuit and a signal circuit from the TCM. Each signal circuit for each gear selector position will have either a voltage reading of 0.70-0.96 V indicting On or 1.68-2.38 V indicating Off. The voltage values on each internal mode switch circuit will change and are dependent on the position of the gear selector. The state of each internal mode switch A/B/C/P/S signal circuit is displayed on the scan tool.