What Does B1749 Mean?
This code indicates the Body Control Module (BCM) or Transmission Control Module (TCM) has detected an abnormal voltage or signal from the park/neutral position switch circuit. The switch informs the vehicle's control modules when the transmission is in park or neutral, which is critical for starting the engine and preventing rollaway. The module detected either an open circuit, short circuit, or implausible signal from this safety-critical switch.
Safety Warning
This is a critical safety issue that may prevent the vehicle from starting or allow it to start in gear, creating a rollaway hazard. The vehicle should not be driven until repaired, and parking brake must always be engaged as the park position may not be properly recognized by the control modules.
Common Causes
45%
Faulty park/neutral position switch with internal wear or contact failure
30%
Damaged or corroded wiring harness and connectors between switch and control module
15%
Misadjusted or loose park/neutral switch mounting causing improper contact alignment
10%
Failed Body Control Module or Transmission Control Module with internal circuit fault
Diagnostic Steps
1
Step 1: Visually inspect the park/neutral position switch at the transmission for physical damage, loose mounting, oil contamination, and verify connector is fully seated with no corrosion or bent pins
2
Step 2: Using a digital multimeter, backprobe the switch connector with the key on and engine off, cycle the shifter through all gear positions while monitoring voltage/resistance changes according to manufacturer specifications (typically 0-5V range or specific resistance values)
3
Step 3: Check continuity and resistance of the wiring harness between the park/neutral switch and the BCM/TCM connector, looking for opens, shorts to ground, or shorts to power (should read less than 5 ohms for continuity)
4
Step 4: If wiring and voltage signals are correct, remove and inspect the park/neutral switch for internal damage, worn contacts, or mechanical binding, and compare resistance values across all gear positions to specifications
5
Step 5: If switch is functioning correctly, check the switch adjustment by loosening mounting bolts and repositioning while monitoring live data to ensure proper signal at each detent position
6
Step 6: Clear codes, test drive through all gear ranges, verify proper engine starting only in park/neutral, and confirm backup lights operate correctly in reverse to validate repair
Estimated Repair Cost
$150 - $650
Parts + labor, varies by vehicle and location
This code indicates the Body Control Module (BCM) or Transmission Control Module (TCM) has detected an abnormal voltage or signal from the park/neutral position switch circuit. The switch informs the vehicle's control modules when the transmission is in park or neutral, which is critical for startin...
The most common cause of B1749 (Park/Neutral Switch Circuit Failure) is: Faulty park/neutral position switch with internal wear or contact failure
Typical repair costs for B1749 range from $150 to $650, depending on the vehicle, location, and whether you do it yourself or go to a shop.
This is a critical safety issue that may prevent the vehicle from starting or allow it to start in gear, creating a rollaway hazard. The vehicle should not be driven until repaired, and parking brake must always be engaged as the park position may not be properly recognized by the control modules.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1749 to identify the root cause.
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Quick Info
Category
Body
System
Transmission Control and Starting System
Difficulty
Type
Manufacturer
Recommended Tools
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