Code
C1238
Generic
C — Chassis
ABS Hydraulic Pressure Differential Switch Input Circuit Failure
AI status
Completed
Completed
100%
Causes
- Open, short or high resistance in the switch wiring harness
- Corroded, loose or contaminated connector at the switch or ABS module
- Failed hydraulic pressure differential switch (internal contact failure)
- Faulty ABS control module input or wiring to module
- Water intrusion or physical damage to harness/connector
- Related blown fuse, relay or poor ground
Symptoms
- ABS warning lamp ON (may be accompanied by traction control/Stability light)
- ABS system disabled — loss of ABS/traction control functionality
- Possible illuminated brake warning lamp
- Noisy or continuous ABS pump operation in some cases
- Possible changes in brake pedal feel or ABS intervention not occurring
What to check
- Read and record ABS codes and freeze frame data with a scan tool
- Visually inspect switch connector and wiring for corrosion, damage, pin push-out or water intrusion
- Wiggle test wiring while monitoring live data or scan tool for circuit changes
- Check for proper power (fused), ground, and reference voltage at the switch connector with key ON
- Measure signal voltage or continuity between switch and ABS module connector
- Check fuses/relays related to ABS module and pump
Signal parameters
- Reference voltage typically 5 V (varies by manufacturer) present at the switch with ignition ON
- Switch output: near 0 V (ground) when closed or providing continuity to ground; near reference voltage (≈4.5–5 V) when open — consult vehicle-specific data
- Open-circuit resistance: effectively infinite (no continuity) when switch open; closed-circuit resistance: typically
- Intermittent switching when pressure differential threshold is crossed — live-data should toggle state when system pressure changes
Diagnostic algorithm
- Connect a capable ABS scan tool, record C1238 and any other ABS or powertrain codes, and note freeze frame/live data.
- Visually inspect the hydraulic pressure differential switch, harness, and connector for corrosion, damage, or fluid exposure. Repair visible damage.
- With ignition ON (engine off), backprobe the switch connector: verify reference voltage, signal voltage, and ground presence according to vehicle data.
- Wiggle the wiring harness and connector while watching live data or meter for intermittent faults. Repair or secure any failing wiring.
- Check continuity between the switch signal/ground pins and the ABS module connector. Repair any open/shorts. Typical continuity to ground when switch closed, open when switch open.
- If wiring and connectors are good, bench-test or replace the hydraulic pressure differential switch. Re-test after replacement.
- If replacement switch and repaired wiring do not clear the code, test/inspect the ABS module power, grounds, and CAN communication. Substitute or repair module only after eliminating wiring/switch issues.
- Clear codes, perform road test or pressure-actuation test to verify correct switch operation and ensure code does not return.
Likely causes
- Damaged or corroded connector at the differential pressure switch
- Open or shorted signal or ground circuit between switch and ABS module
- Failed pressure differential switch
- Short to battery or chassis ground in harness near switch
Fault status
Status
ABS control module detected a failure in the input circuit for the hydraulic pressure differential switch. Check wiring, connector, and switch; replace parts as needed and verify system operation.
Repair difficulty: Medium
Diagnostic time: 1.0 - 2.5 hours
Similar codes
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Code
C1238
HUMMER
C — Chassis
Brake Thermal Model Exceeded
AI status
Completed
Completed
100%
Causes
- Open, short or high resistance in the switch wiring harness
- Corroded, loose or contaminated connector at the switch or ABS module
- Failed hydraulic pressure differential switch (internal contact failure)
- Faulty ABS control module input or wiring to module
- Water intrusion or physical damage to harness/connector
- Related blown fuse, relay or poor ground
Symptoms
- ABS warning lamp ON (may be accompanied by traction control/Stability light)
- ABS system disabled — loss of ABS/traction control functionality
- Possible illuminated brake warning lamp
- Noisy or continuous ABS pump operation in some cases
- Possible changes in brake pedal feel or ABS intervention not occurring
What to check
- Read and record ABS codes and freeze frame data with a scan tool
- Visually inspect switch connector and wiring for corrosion, damage, pin push-out or water intrusion
- Wiggle test wiring while monitoring live data or scan tool for circuit changes
- Check for proper power (fused), ground, and reference voltage at the switch connector with key ON
- Measure signal voltage or continuity between switch and ABS module connector
- Check fuses/relays related to ABS module and pump
Signal parameters
- Reference voltage typically 5 V (varies by manufacturer) present at the switch with ignition ON
- Switch output: near 0 V (ground) when closed or providing continuity to ground; near reference voltage (≈4.5–5 V) when open — consult vehicle-specific data
- Open-circuit resistance: effectively infinite (no continuity) when switch open; closed-circuit resistance: typically
- Intermittent switching when pressure differential threshold is crossed — live-data should toggle state when system pressure changes
Diagnostic algorithm
- Connect a capable ABS scan tool, record C1238 and any other ABS or powertrain codes, and note freeze frame/live data.
- Visually inspect the hydraulic pressure differential switch, harness, and connector for corrosion, damage, or fluid exposure. Repair visible damage.
- With ignition ON (engine off), backprobe the switch connector: verify reference voltage, signal voltage, and ground presence according to vehicle data.
- Wiggle the wiring harness and connector while watching live data or meter for intermittent faults. Repair or secure any failing wiring.
- Check continuity between the switch signal/ground pins and the ABS module connector. Repair any open/shorts. Typical continuity to ground when switch closed, open when switch open.
- If wiring and connectors are good, bench-test or replace the hydraulic pressure differential switch. Re-test after replacement.
- If replacement switch and repaired wiring do not clear the code, test/inspect the ABS module power, grounds, and CAN communication. Substitute or repair module only after eliminating wiring/switch issues.
- Clear codes, perform road test or pressure-actuation test to verify correct switch operation and ensure code does not return.
Likely causes
- Damaged or corroded connector at the differential pressure switch
- Open or shorted signal or ground circuit between switch and ABS module
- Failed pressure differential switch
- Short to battery or chassis ground in harness near switch
Fault status
Status
ABS control module detected a failure in the input circuit for the hydraulic pressure differential switch. Check wiring, connector, and switch; replace parts as needed and verify system operation.
Repair difficulty: Medium
Diagnostic time: 1.0 - 2.5 hours
Similar codes
Repair manuals
Manual library for HUMMER
138
Browse 138 HUMMER manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.
HUMMER
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HUMMER: 2009
-
HUMMER: 2008
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HUMMER: 2007
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HUMMER: 2005
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HUMMER: 2004
-
HUMMER: 2000
-
HUMMER: 1999
-
HUMMER: 1994
-
HUMMER: 1993
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Code
C1238
HYUNDAI
C — Chassis
Front Height Sensor High
AI status
Completed
Completed
100%
Causes
- Open, short or high resistance in the switch wiring harness
- Corroded, loose or contaminated connector at the switch or ABS module
- Failed hydraulic pressure differential switch (internal contact failure)
- Faulty ABS control module input or wiring to module
- Water intrusion or physical damage to harness/connector
- Related blown fuse, relay or poor ground
Symptoms
- ABS warning lamp ON (may be accompanied by traction control/Stability light)
- ABS system disabled — loss of ABS/traction control functionality
- Possible illuminated brake warning lamp
- Noisy or continuous ABS pump operation in some cases
- Possible changes in brake pedal feel or ABS intervention not occurring
What to check
- Read and record ABS codes and freeze frame data with a scan tool
- Visually inspect switch connector and wiring for corrosion, damage, pin push-out or water intrusion
- Wiggle test wiring while monitoring live data or scan tool for circuit changes
- Check for proper power (fused), ground, and reference voltage at the switch connector with key ON
- Measure signal voltage or continuity between switch and ABS module connector
- Check fuses/relays related to ABS module and pump
Signal parameters
- Reference voltage typically 5 V (varies by manufacturer) present at the switch with ignition ON
- Switch output: near 0 V (ground) when closed or providing continuity to ground; near reference voltage (≈4.5–5 V) when open — consult vehicle-specific data
- Open-circuit resistance: effectively infinite (no continuity) when switch open; closed-circuit resistance: typically
- Intermittent switching when pressure differential threshold is crossed — live-data should toggle state when system pressure changes
Diagnostic algorithm
- Connect a capable ABS scan tool, record C1238 and any other ABS or powertrain codes, and note freeze frame/live data.
- Visually inspect the hydraulic pressure differential switch, harness, and connector for corrosion, damage, or fluid exposure. Repair visible damage.
- With ignition ON (engine off), backprobe the switch connector: verify reference voltage, signal voltage, and ground presence according to vehicle data.
- Wiggle the wiring harness and connector while watching live data or meter for intermittent faults. Repair or secure any failing wiring.
- Check continuity between the switch signal/ground pins and the ABS module connector. Repair any open/shorts. Typical continuity to ground when switch closed, open when switch open.
- If wiring and connectors are good, bench-test or replace the hydraulic pressure differential switch. Re-test after replacement.
- If replacement switch and repaired wiring do not clear the code, test/inspect the ABS module power, grounds, and CAN communication. Substitute or repair module only after eliminating wiring/switch issues.
- Clear codes, perform road test or pressure-actuation test to verify correct switch operation and ensure code does not return.
Likely causes
- Damaged or corroded connector at the differential pressure switch
- Open or shorted signal or ground circuit between switch and ABS module
- Failed pressure differential switch
- Short to battery or chassis ground in harness near switch
Fault status
Status
ABS control module detected a failure in the input circuit for the hydraulic pressure differential switch. Check wiring, connector, and switch; replace parts as needed and verify system operation.
Repair difficulty: Medium
Diagnostic time: 1.0 - 2.5 hours
Similar codes
Repair manuals
Manual library for HYUNDAI
371
Browse 371 HYUNDAI manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.
HYUNDAI
-
HYUNDAI: 2023
-
Elantra
-
Elantra N
-
Kona N
-
Tucson
- Hybrid Blue
- Hybrid Limited
- Hybrid SEL Convenience
- Limited, Eng CD G4EN, 4WD
- Limited, Eng CD G4EN, FWD
- Limited, Eng CD G4KN, 4WD
- Limited, Eng CD G4KN, FWD
- N Line, Eng CD G4EN, 4WD
- N Line, Eng CD G4EN, FWD
- N Line, Eng CD G4KN, 4WD
- N Line, Eng CD G4KN, FWD
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- Plug-In Hybrid SEL
- SE, Eng CD G4EN, 4WD
- SE, Eng CD G4EN, FWD
- SE, Eng CD G4KN, 4WD
- SE, Eng CD G4KN, FWD
- SEL, Eng CD G4EN, 4WD
- SEL, Eng CD G4EN, FWD
- SEL, Eng CD G4KN, 4WD
- SEL, Eng CD G4KN, FWD
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- XRT, Eng CD G4EN, FWD
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- XRT, Eng CD G4KN, FWD
-
-
HYUNDAI: 2022
-
Elantra N
-
Kona N
-
Veloster N
-
HYUNDAI: 2021
-
Veloster N
-
HYUNDAI: 2020
-
Palisade
-
Veloster N
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Code
C1238
Other
C — Chassis
ABS Hydraulic Pressure Differential Switch Input Circuit Failure
AI status
Completed
Completed
100%
Causes
- Open, short or high resistance in the switch wiring harness
- Corroded, loose or contaminated connector at the switch or ABS module
- Failed hydraulic pressure differential switch (internal contact failure)
- Faulty ABS control module input or wiring to module
- Water intrusion or physical damage to harness/connector
- Related blown fuse, relay or poor ground
Symptoms
- ABS warning lamp ON (may be accompanied by traction control/Stability light)
- ABS system disabled — loss of ABS/traction control functionality
- Possible illuminated brake warning lamp
- Noisy or continuous ABS pump operation in some cases
- Possible changes in brake pedal feel or ABS intervention not occurring
What to check
- Read and record ABS codes and freeze frame data with a scan tool
- Visually inspect switch connector and wiring for corrosion, damage, pin push-out or water intrusion
- Wiggle test wiring while monitoring live data or scan tool for circuit changes
- Check for proper power (fused), ground, and reference voltage at the switch connector with key ON
- Measure signal voltage or continuity between switch and ABS module connector
- Check fuses/relays related to ABS module and pump
Signal parameters
- Reference voltage typically 5 V (varies by manufacturer) present at the switch with ignition ON
- Switch output: near 0 V (ground) when closed or providing continuity to ground; near reference voltage (≈4.5–5 V) when open — consult vehicle-specific data
- Open-circuit resistance: effectively infinite (no continuity) when switch open; closed-circuit resistance: typically
- Intermittent switching when pressure differential threshold is crossed — live-data should toggle state when system pressure changes
Diagnostic algorithm
- Connect a capable ABS scan tool, record C1238 and any other ABS or powertrain codes, and note freeze frame/live data.
- Visually inspect the hydraulic pressure differential switch, harness, and connector for corrosion, damage, or fluid exposure. Repair visible damage.
- With ignition ON (engine off), backprobe the switch connector: verify reference voltage, signal voltage, and ground presence according to vehicle data.
- Wiggle the wiring harness and connector while watching live data or meter for intermittent faults. Repair or secure any failing wiring.
- Check continuity between the switch signal/ground pins and the ABS module connector. Repair any open/shorts. Typical continuity to ground when switch closed, open when switch open.
- If wiring and connectors are good, bench-test or replace the hydraulic pressure differential switch. Re-test after replacement.
- If replacement switch and repaired wiring do not clear the code, test/inspect the ABS module power, grounds, and CAN communication. Substitute or repair module only after eliminating wiring/switch issues.
- Clear codes, perform road test or pressure-actuation test to verify correct switch operation and ensure code does not return.
Likely causes
- Damaged or corroded connector at the differential pressure switch
- Open or shorted signal or ground circuit between switch and ABS module
- Failed pressure differential switch
- Short to battery or chassis ground in harness near switch
Fault status
Status
ABS control module detected a failure in the input circuit for the hydraulic pressure differential switch. Check wiring, connector, and switch; replace parts as needed and verify system operation.
Repair difficulty: Medium
Diagnostic time: 1.0 - 2.5 hours
Similar codes
Repair manuals
Brands with available manuals
9,609
The library contains 9,609 repair and diagnostic manuals. Choose a brand to open the full manual tree by year, model and trim.
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
0
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0
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