What Does B1657 Mean?
This code indicates that the Body Control Module (BCM) or seat control module has detected a short to battery voltage in the circuit controlling the driver's seat rear vertical adjustment motor (upward movement). This means the circuit is seeing constant battery voltage (12V+) when it should be at ground or a lower reference voltage, typically caused by damaged wiring or a failed component creating an unintended power supply path.
Common Causes
45%
Damaged or chafed wiring harness between seat control module and seat motor, causing wire insulation to contact battery voltage
30%
Failed seat rear adjustment motor with internal short to power creating feedback voltage
15%
Corroded or damaged connector pins at seat motor or control module creating cross-circuit contact
10%
Failed seat control module with internal driver circuit malfunction
Diagnostic Steps
1
Step 1: Perform visual inspection of all wiring and connectors between the seat control module and driver seat rear adjustment motor, looking for chafed insulation, pinched wires under seat tracks, damaged connector housings, or signs of water intrusion
2
Step 2: Disconnect the seat rear adjustment motor connector and use a digital multimeter to measure voltage on the circuit wire specified in manufacturer wiring diagram (typically the motor up control wire) with ignition on - reading should be 0V or ground reference, not battery voltage
3
Step 3: If battery voltage is present at disconnected motor connector, disconnect the seat control module connector and retest - if voltage disappears, module is faulty; if voltage remains, trace wiring harness for short to power between connectors
4
Step 4: If no voltage found with motor disconnected, measure resistance of motor windings (typically 2-6 ohms between terminals) and check for short to ground on motor housing - replace motor if shorted internally
5
Step 5: Reconnect all components, clear codes, and cycle seat adjustment functions through full range while monitoring live data for voltage spikes or abnormal current draw exceeding 10-15 amps
6
Step 6: Perform final verification by operating seat rear adjustment in both directions multiple times to confirm proper operation and verify code does not return
Estimated Repair Cost
$150 - $650
Parts + labor, varies by vehicle and location
This code indicates that the Body Control Module (BCM) or seat control module has detected a short to battery voltage in the circuit controlling the driver's seat rear vertical adjustment motor (upward movement). This means the circuit is seeing constant battery voltage (12V+) when it should be at g...
The most common cause of B1657 (Seat Driver Rear Up Circuit Short To Battery) is: Damaged or chafed wiring harness between seat control module and seat motor, causing wire insulation to contact battery voltage
Typical repair costs for B1657 range from $150 to $650, depending on the vehicle, location, and whether you do it yourself or go to a shop.
This fault does not affect vehicle safety or drivability and the vehicle is safe to operate. The driver's seat rear vertical adjustment may not function properly or may move unexpectedly, but primary seating position typically remains functional.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1657 to identify the root cause.
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Quick Info
Category
Body
System
Power Seat Control System
Difficulty
Type
Manufacturer
Recommended Tools
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