What Does B1588 Mean?
This code indicates that the Body Control Module (BCM) has detected an open circuit in the autolamp delay increase switch or its associated wiring. The autolamp system is designed to keep exterior lighting illuminated for a set period after the vehicle is turned off and exited. An open circuit means the BCM cannot receive the signal to increase this delay timer, suggesting a broken wire, failed switch, or poor connector contact in the delay increase circuit.
Common Causes
45%
Open or damaged wiring between the autolamp delay switch and BCM, including corroded or disconnected connectors
30%
Failed autolamp delay increase switch or multi-function switch assembly
15%
Corroded or loose ground connection in the autolamp circuit
10%
Failed or damaged Body Control Module with internal circuit fault
Diagnostic Steps
1
Step 1: Perform a visual inspection of the autolamp delay switch (typically located on the headlight switch or multi-function switch) and its connector for signs of damage, corrosion, or loose connections. Check connector pins for bent, pushed back, or corroded terminals.
2
Step 2: Using a digital multimeter, check for continuity in the wiring between the autolamp delay switch connector and the BCM connector with the switch disconnected. Resistance should be less than 1 ohm. Also verify the circuit is not shorted to ground (should read infinite resistance to ground).
3
Step 3: With the switch connected and ignition on, measure voltage at the switch input terminal (should have battery voltage or 5V reference depending on manufacturer). Test switch operation by actuating the delay increase function and measuring continuity or resistance change across the appropriate switch terminals per manufacturer specifications.
4
Step 4: Check the ground circuit for the autolamp system by measuring voltage drop between the switch ground and battery negative with system activated. Voltage drop should be less than 0.1V. Clean and tighten ground connections if excessive resistance is found.
5
Step 5: If all wiring and switch tests pass, monitor BCM input signal using bi-directional controls or live data to verify the BCM is capable of receiving inputs. If BCM does not recognize switch inputs with known good wiring and switch, BCM replacement may be necessary.
6
Step 6: After repair, clear codes, cycle the autolamp delay increase function multiple times, and verify proper operation of the delayed lighting feature. Road test and re-scan to confirm no code return.
Estimated Repair Cost
$100 - $450
Parts + labor, varies by vehicle and location
This code indicates that the Body Control Module (BCM) has detected an open circuit in the autolamp delay increase switch or its associated wiring. The autolamp system is designed to keep exterior lighting illuminated for a set period after the vehicle is turned off and exited. An open circuit means...
The most common cause of B1588 (Autolamp Delay Increase Circuit Open) is: Open or damaged wiring between the autolamp delay switch and BCM, including corroded or disconnected connectors
Typical repair costs for B1588 range from $100 to $450, depending on the vehicle, location, and whether you do it yourself or go to a shop.
This code does not affect vehicle safety or drivability. The vehicle can be driven normally, though the convenience feature of adjusting the autolamp delay period will not function. Repair can be scheduled at the owner's convenience.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1588 to identify the root cause.
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Quick Info
Category
Body
System
Exterior Lighting Control System
Difficulty
Type
Manufacturer
Recommended Tools
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