Code
C1240
Generic
C — Chassis
ABS Hydraulic Pressure Differential Switch Input Short Circuit To Battery
Views:
UK: 16
EN: 30
RU: 17
AI status
Completed
Completed
100%
Causes
- Damaged or chafed wiring harness shorted to battery positive
- Corroded or pushed-back connector pin contacting battery voltage
- Failed/shorted hydraulic pressure differential switch (internal short)
- Faulty ABS/ESC control module input driver
- Aftermarket electrical accessories or incorrect repairs that tapped into the circuit
- Blown or incorrect fuse routing power into the sensor circuit
Symptoms
- ABS warning lamp illuminated
- Traction/stability control lamp may also illuminate
- ABS/ESC functionality degraded or disabled
- Possible stored or active related DTCs in ABS module
- No engine drivability symptoms (braking feel may be normal until ABS intervenes)
What to check
- Read ABS module freeze frame and full DTC list with a scan tool; note related codes
- Visually inspect switch connector and harness for damage, corrosion, or pin displacement
- Backprobe the switch connector with ignition ON and measure voltage at the signal pin
- Check continuity from signal circuit to battery positive (detect short to B+)
- Disconnect the switch; see if the code clears or changes when key cycled
- Inspect fuses and any inline connectors or junctions that feed the sensor circuit
Signal parameters
- Expected: Open/low current signal when switch not activated; measured voltage typically near 0 V when pulled to ground
- Expected: Battery voltage (~12 V) only present on the circuit when deliberately powered (reference/supply pin), not on the switch signal input
- Fault: Signal pin measures near battery voltage (~11–14 V) when it should be low or high-impedance
- Resistance: When switch closed, low resistance (< a few ohms); when open, high resistance (kΩ or open circuit) — check service data for exact values
Diagnostic algorithm
- Use a scan tool to confirm C1240 and record freeze frame data and any related ABS codes.
- Visually inspect harness, switch connector, and ABS module connector for damage, corrosion, or signs of heat.
- With ignition ON (engine OFF), backprobe the switch connector signal terminal and measure DC voltage vs. vehicle ground. Note whether it is held at battery voltage.
- Disconnect the switch connector. Clear codes, then cycle ignition and check if C1240 returns. If code does not return with switch disconnected, suspect the switch wiring or switch itself.
- With harness disconnected from switch, test for short to battery: measure continuity between the signal wire and battery positive. Continuity indicates a short to B+ in the wiring or connectors.
- Inspect and repair any wiring that shows short to battery (locate where harness contacts a live conductor, repair insulation, replace wire or connector as needed).
Likely causes
- Wiring insulation abrasion where harness contacts chassis or hot circuit
- Connector contamination or bent pin contacting B+ terminal
- Switch failed internally and is feeding battery voltage back to module
- Previous poor repair or connector mating issue near brake hydraulic area
Fault status
Status
C1240 — ABS Hydraulic Pressure Differential Switch Input Short to Battery detected. ABS/ESC control module has identified excessive voltage on the switch input; ABS functionality may be reduced.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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Code
C1240
HYUNDAI
C — Chassis
Rear Height Sensor Abnormal. | Second Speed Input Fault | Signal SAS_Angle not Valid or Signal SAS MsgCount or Checksum not Correct
Views:
UK: 13
EN: 24
RU: 17
AI status
Completed
Completed
100%
Causes
- Damaged or chafed wiring harness shorted to battery positive
- Corroded or pushed-back connector pin contacting battery voltage
- Failed/shorted hydraulic pressure differential switch (internal short)
- Faulty ABS/ESC control module input driver
- Aftermarket electrical accessories or incorrect repairs that tapped into the circuit
- Blown or incorrect fuse routing power into the sensor circuit
Symptoms
- ABS warning lamp illuminated
- Traction/stability control lamp may also illuminate
- ABS/ESC functionality degraded or disabled
- Possible stored or active related DTCs in ABS module
- No engine drivability symptoms (braking feel may be normal until ABS intervenes)
What to check
- Read ABS module freeze frame and full DTC list with a scan tool; note related codes
- Visually inspect switch connector and harness for damage, corrosion, or pin displacement
- Backprobe the switch connector with ignition ON and measure voltage at the signal pin
- Check continuity from signal circuit to battery positive (detect short to B+)
- Disconnect the switch; see if the code clears or changes when key cycled
- Inspect fuses and any inline connectors or junctions that feed the sensor circuit
Signal parameters
- Expected: Open/low current signal when switch not activated; measured voltage typically near 0 V when pulled to ground
- Expected: Battery voltage (~12 V) only present on the circuit when deliberately powered (reference/supply pin), not on the switch signal input
- Fault: Signal pin measures near battery voltage (~11–14 V) when it should be low or high-impedance
- Resistance: When switch closed, low resistance (< a few ohms); when open, high resistance (kΩ or open circuit) — check service data for exact values
Diagnostic algorithm
- Use a scan tool to confirm C1240 and record freeze frame data and any related ABS codes.
- Visually inspect harness, switch connector, and ABS module connector for damage, corrosion, or signs of heat.
- With ignition ON (engine OFF), backprobe the switch connector signal terminal and measure DC voltage vs. vehicle ground. Note whether it is held at battery voltage.
- Disconnect the switch connector. Clear codes, then cycle ignition and check if C1240 returns. If code does not return with switch disconnected, suspect the switch wiring or switch itself.
- With harness disconnected from switch, test for short to battery: measure continuity between the signal wire and battery positive. Continuity indicates a short to B+ in the wiring or connectors.
- Inspect and repair any wiring that shows short to battery (locate where harness contacts a live conductor, repair insulation, replace wire or connector as needed).
Likely causes
- Wiring insulation abrasion where harness contacts chassis or hot circuit
- Connector contamination or bent pin contacting B+ terminal
- Switch failed internally and is feeding battery voltage back to module
- Previous poor repair or connector mating issue near brake hydraulic area
Fault status
Status
C1240 — ABS Hydraulic Pressure Differential Switch Input Short to Battery detected. ABS/ESC control module has identified excessive voltage on the switch input; ABS functionality may be reduced.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
Similar codes
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👍 Like
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Code
C1240
Other
C — Chassis
ABS Hydraulic Pressure Differential Switch Input Short Circuit To Battery
Views:
UK: 19
EN: 32
RU: 21
AI status
Completed
Completed
100%
Causes
- Damaged or chafed wiring harness shorted to battery positive
- Corroded or pushed-back connector pin contacting battery voltage
- Failed/shorted hydraulic pressure differential switch (internal short)
- Faulty ABS/ESC control module input driver
- Aftermarket electrical accessories or incorrect repairs that tapped into the circuit
- Blown or incorrect fuse routing power into the sensor circuit
Symptoms
- ABS warning lamp illuminated
- Traction/stability control lamp may also illuminate
- ABS/ESC functionality degraded or disabled
- Possible stored or active related DTCs in ABS module
- No engine drivability symptoms (braking feel may be normal until ABS intervenes)
What to check
- Read ABS module freeze frame and full DTC list with a scan tool; note related codes
- Visually inspect switch connector and harness for damage, corrosion, or pin displacement
- Backprobe the switch connector with ignition ON and measure voltage at the signal pin
- Check continuity from signal circuit to battery positive (detect short to B+)
- Disconnect the switch; see if the code clears or changes when key cycled
- Inspect fuses and any inline connectors or junctions that feed the sensor circuit
Signal parameters
- Expected: Open/low current signal when switch not activated; measured voltage typically near 0 V when pulled to ground
- Expected: Battery voltage (~12 V) only present on the circuit when deliberately powered (reference/supply pin), not on the switch signal input
- Fault: Signal pin measures near battery voltage (~11–14 V) when it should be low or high-impedance
- Resistance: When switch closed, low resistance (< a few ohms); when open, high resistance (kΩ or open circuit) — check service data for exact values
Diagnostic algorithm
- Use a scan tool to confirm C1240 and record freeze frame data and any related ABS codes.
- Visually inspect harness, switch connector, and ABS module connector for damage, corrosion, or signs of heat.
- With ignition ON (engine OFF), backprobe the switch connector signal terminal and measure DC voltage vs. vehicle ground. Note whether it is held at battery voltage.
- Disconnect the switch connector. Clear codes, then cycle ignition and check if C1240 returns. If code does not return with switch disconnected, suspect the switch wiring or switch itself.
- With harness disconnected from switch, test for short to battery: measure continuity between the signal wire and battery positive. Continuity indicates a short to B+ in the wiring or connectors.
- Inspect and repair any wiring that shows short to battery (locate where harness contacts a live conductor, repair insulation, replace wire or connector as needed).
Likely causes
- Wiring insulation abrasion where harness contacts chassis or hot circuit
- Connector contamination or bent pin contacting B+ terminal
- Switch failed internally and is feeding battery voltage back to module
- Previous poor repair or connector mating issue near brake hydraulic area
Fault status
Status
C1240 — ABS Hydraulic Pressure Differential Switch Input Short to Battery detected. ABS/ESC control module has identified excessive voltage on the switch input; ABS functionality may be reduced.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
Similar codes
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
0
👎 Dislike
0
Send to email