B1535

What Does Code B1535 Mean?

DTC B1535 signifies a detected circuit failure associated with the “Memory 2 Switch.” In most automotive applications, “Memory Switches” are integral components of driver convenience systems, primarily found in power seating, power mirrors, and power steering column adjustment modules. These systems allow drivers to store and recall preferred positions for various vehicle components. The BCM (Body Control Module), DSM (Driver Seat Module), or a similar control module responsible for these functions, continuously monitors the electrical integrity of the circuits connected to these input switches.

When the control module detects an electrical anomaly on the dedicated circuit for the “Memory 2” switch—such as an open circuit (break in wiring), a short to ground, a short to voltage, or an out-of-specification resistance value—it interprets this as a circuit malfunction. This condition prevents the control module from accurately receiving the input signal from the Memory 2 switch, thereby inhibiting the recall of previously stored settings corresponding to “Memory 2.” The code indicates a fault with the electrical path, which could involve the switch itself, the connecting wiring, or the input stage of the control module.

Common Symptoms

• Inability to recall “Memory 2” settings: The primary symptom is that pressing the Memory 2 button has no effect on the associated components (e.g., seat, mirrors, steering wheel).
• No tactile or audible feedback from the Memory 2 button: The button may not illuminate or produce a confirmation sound when pressed.
• Intermittent functionality of other memory presets: Though less common, a shared power or ground circuit fault could potentially affect other memory functions.
• Warning message on the instrument cluster: Some advanced systems may display a message such as “Memory Function Unavailable” or “Seat Memory Malfunction.”

What Causes the Code B1535?

• Faulty Memory 2 Switch Assembly: Internal electrical failure within the switch, such as worn contacts, a broken return spring, or a damaged internal resistor (common in multiplexed switch systems).
• Wiring Harness Issues: An open circuit (broken wire), a short to ground, a short to voltage, or excessively high resistance in the wiring between the Memory 2 switch and its controlling module (e.g., BCM, DSM). This often occurs in areas prone to movement like door jambs or under seats.
• Corrosion or Contamination: Electrical corrosion or debris within the switch connector, the module connector, or the switch assembly itself, leading to poor electrical contact or an intermittent connection.
• Faulty Control Module Input: Damage to the specific input circuit within the BCM, DSM, or other relevant control module that monitors the Memory 2 switch. This is less common but can occur due to internal component failure or voltage spikes.
• Poor Ground Connection: An inadequate or corroded ground point for the Memory 2 switch circuit, leading to an incorrect voltage signal.

How to Diagnose and Troubleshoot

Diagnosing B1535 requires a systematic approach, utilizing a digital multimeter (DMM) and a diagnostic scan tool capable of reading body control module data.

1. Retrieve and Document DTCs and Freeze Frame Data: Connect an OBD-II scan tool and read all stored DTCs. Note any accompanying codes, especially those related to the Body Control Module (BCM) or Driver Seat Module (DSM). Review freeze frame data to understand the conditions (e.g., battery voltage, vehicle speed) when the code was set.
2. Visual Inspection:
   • Inspect the Memory 2 switch for physical damage, debris, or fluid ingress.
   • Locate the wiring harness connecting the switch to the control module. Carefully inspect for signs of chafing, pinching, cuts, or corrosion, particularly where the harness passes through door jambs or under the seat.
   • Disconnect the switch connector and the control module connector (e.g., BCM, DSM). Inspect pins for bent, pushed-out, or corroded terminals.
3. Scan Tool Live Data Analysis:
   • Access live data parameters for the BCM or DSM. Look for a parameter indicating the state of the “Memory 2 Switch Input.”
   • With the ignition ON and the engine OFF, observe the scanner’s reading while pressing and releasing the Memory 2 button. A healthy circuit should show a distinct change in state (e.g., “OFF” to “ON,” or a voltage change). If no change is observed, or if the reading is erratic, it confirms a circuit fault.
4. Digital Multimeter (DMM) Testing – Circuit Integrity:
   • Isolate the circuit: Disconnect the vehicle battery. Disconnect the Memory 2 switch connector and the control module connector.
   • Continuity Test (Wiring): Using the DMM in ohms mode, test for continuity of the signal wire(s) from the switch connector to the corresponding pin at the control module connector. Resistance should be less than 1.0 ohm. An open circuit (OL or infinite resistance) indicates a broken wire.
   • Short to Ground Test: With the DMM in ohms mode, measure resistance between the signal wire(s) and a known good chassis ground. Resistance should be infinite (OL). A low resistance reading indicates a short to ground. Repeat for power wires.
   • Short to Voltage Test: Reconnect the battery. With the DMM in volts mode, measure voltage on the signal wire(s) at the disconnected switch and module connectors. Ensure no unwanted voltage is present (should be 0V unless it’s a reference voltage circuit).
   • Reference Voltage Check (Module Side): At the control module harness connector (disconnected from the module), identify the reference voltage pin (usually 5V or 12V, consult wiring diagram). Reconnect the battery and measure voltage at this pin. Verify it’s within specifications.
5. Digital Multimeter (DMM) Testing – Switch Functionality:
   • With the Memory 2 switch disconnected from its harness, use the DMM in ohms mode. Consult the vehicle’s wiring diagram for specific pinouts.
   • Simple ON/OFF Switch: Test continuity across the switch terminals while pressing and releasing the button. It should show continuity when pressed (near 0 ohms) and open (OL) when released.
   • Multiplexed/Resistor Ladder Switch: Many modern systems use a single signal wire with multiple buttons, each adding a specific resistance to the circuit. Measure the resistance across the switch terminals for the Memory 2 function. Compare the measured resistance to the specified value in the service manual. An incorrect or infinite resistance indicates an internal switch failure.

Recommended Repairs and Solutions

Based on the diagnostic findings, the following repairs are typically recommended:

1. Replace the Memory 2 Switch Assembly: If DMM testing unequivocally identifies the switch as faulty (e.g., incorrect resistance, no continuity, or internal damage), replace the entire switch assembly. Ensure the replacement part is specific to the vehicle’s trim level and features.
2. Repair or Replace Wiring Harness: If the diagnostic procedure points to an open circuit, short, or high resistance within the wiring, the harness must be repaired. For open or shorted wires, use appropriate gauge wire, solder connections, and seal with heat-shrink tubing. If damage is extensive or in multiple locations, replacing the affected section of the harness might be more practical and reliable.
3. Clean Connectors and Terminals: If corrosion or poor contact at connectors is identified, use a specialized electrical contact cleaner to meticulously clean all terminals. After cleaning, apply a small amount of dielectric grease to prevent future corrosion and ensure good electrical contact. Re-seat connectors firmly.
4. Replace the Control Module (BCM/DSM): This is a last resort, to be performed only after all other possibilities (switch, wiring, power, ground) have been thoroughly tested and ruled out. A faulty control module requires replacement and often subsequent programming or configuration with a capable scan tool specific to the vehicle manufacturer.
5. Verify Ground Integrity: If a poor ground was identified, clean the ground point and ensure a solid, low-resistance connection to the chassis or body.

Mechanics’ Tips:

• Always refer to the manufacturer’s specific wiring diagrams and service information for accurate pinouts, wire colors, and expected voltage/resistance values for the vehicle in question.
• When dealing with memory functions, especially seats, be mindful of potential airbag system wiring. Always disconnect the battery and allow sufficient discharge time (typically 15-30 minutes) before working on components near airbag modules or wiring.
• If the vehicle uses a multiplexed switch system, understanding the specific resistance values for each switch position is critical for accurate diagnosis.
• After any repair, clear the DTCs using an OBD-II scanner and test the Memory 2 function multiple times to confirm the repair is successful and the code does not return.
• Check for any applicable Technical Service Bulletins (TSBs) from the manufacturer that might address known issues with memory seat/mirror/column functions for the specific year, make, and model.