What Does P1729 Mean?
The starter interlock circuit is detecting battery voltage when it should be grounded or at low voltage. This safety circuit prevents the starter from engaging under certain conditions, and a short to positive indicates a wiring fault.
Common Causes
40%
Damaged wiring harness causing short to battery positive
30%
Faulty neutral safety switch or range sensor internal short
15%
Failed clutch pedal position switch (manual transmission)
10%
Corroded or damaged connector at switch or module
5%
Powertrain control module internal fault
Diagnostic Steps
1
Step 1: Inspect starter interlock circuit wiring for chafing, pinching, or damage
2
Step 2: Disconnect neutral safety/range sensor and recheck for short to B+ at harness side
3
Step 3: Test neutral safety switch or clutch pedal position switch for proper resistance and operation
4
Step 4: Check for aftermarket accessories or remote starters that may have improperly tapped into circuit
5
Step 5: Use wiring diagram to trace circuit and isolate short location between switch and PCM
Estimated Repair Cost
$100 - $500
Parts + labor, varies by vehicle and location
The starter interlock circuit is detecting battery voltage when it should be grounded or at low voltage. This safety circuit prevents the starter from engaging under certain conditions, and a short to positive indicates a wiring fault.
The most common cause of P1729 (Starter Interlock Circ. Short to B+) is: Damaged wiring harness causing short to battery positive
Typical repair costs for P1729 range from $100 to $500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
May prevent vehicle from starting or allow starting in gear, creating a serious safety hazard. Do not drive until repaired; vehicle may lurch forward when starting.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1729 to identify the root cause.
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Quick Info
Category
Powertrain
System
Starting System
Difficulty
Type
Manufacturer
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