Code
B1378
ALFA ROMEO
B — Body
Oil change warning lamp circuit short to ground
Views:
UK: 3
EN: 6
RU: 4
AI status
Completed
Completed
100%
Causes
- Damaged wiring insulation with conductor contacting chassis ground
- Corroded or water-damaged lamp socket or connector
- Shorted lamp bulb or LED module
- Poor/loose ground or additional aftermarket grounding/modification
- Faulty instrument cluster or body control module (mis-driving the circuit)
- Pinched harness where it passes through body panels or bulkheads
Symptoms
- Oil change or service-wrench/warning lamp illuminated when it should be off
- Unable to reset service interval or lamp remains lit after reset attempt
- Related instrument cluster lamp anomalies or intermittent lamp behavior
- Possible battery drain if short is permanent
- Stored B1378 and possibly related lamp circuit DTCs in module memory
What to check
- Retrieve DTCs and freeze-frame data with a diagnostic scanner; note ignition and engine conditions when fault set
- Visually inspect lamp socket, connector, and harness for damage, corrosion, or water ingress
- Inspect ground points and body harness routing for chafe or contact with sharp edges
- Disconnect the instrument cluster or lamp connector and see if the fault clears (to isolate wiring vs. module)
- Measure continuity between lamp feed and chassis ground with ignition off; and resistance of lamp circuit
- Back-probe lamp supply with ignition ON to verify voltage and switching behavior while commanding lamp on/off via scan tool if available
Signal parameters
- Expected: With ignition ON and lamp not commanded, lamp feed should be open circuit to ground (high resistance, e.g., >10 kΩ)
- Expected: When module commands lamp ON, the module provides a ground (low resistance path) or switches supply depending on design; verify OEM wiring diagram
- Short indication: continuous low resistance to ground (
- Voltage: lamp supply should be ~battery voltage (~11–14 V) at the feed terminal when power is present; signal to ground should only be present when commanded by module
Diagnostic algorithm
- Connect a scan tool, read and record DTCs and freeze frame. Confirm B1378 is current or historic.
- Verify symptom: is oil change lamp illuminated? Try servicing/reset procedure to see if lamp clears.
- Visually inspect lamp socket, cluster connector, harness routing and ground points for obvious damage, corrosion or water entry.
- With ignition OFF, disconnect the oil change lamp connector (or instrument cluster connector) and check if the DTC clears or changes after cycling ignition. If fault clears, problem is in wiring/lamp. If not, suspect module.
- Measure resistance between lamp feed and chassis ground (ignition OFF). A low resistance indicates a short to ground.
- With ignition ON, back-probe the lamp feed to check for battery voltage and observe behaviour while commanding the lamp ON/OFF via scan tool. Note if circuit is permanently grounded.
- Perform a wiggle/stress test along the harness while monitoring the circuit for intermittent shorts. Pay attention to bulkhead pass-throughs and areas where harness contacts metal.
- Isolate sections by unplugging intermediate connectors to localize short location. Repair any damaged wires, replace corroded connectors, or re-pin damaged terminals.
- If wiring and connectors check good, consider replacing or bench-testing the instrument cluster/BCM per OEM procedure.
- After repair, clear codes, perform functional test and road/test cycle to ensure the fault does not return.
Likely causes
- Wiring harness chafe in engine bay or dash harness where it rubs on metal
- Corrosion/water ingress at the lamp socket or cluster connector
- Failed lamp/LED inside the cluster causing internal short
- Connector pins pushed out or contacting ground at a mounting point
- Instrument cluster/BCM internal short (less common)
Fault status
Status
Oil change/service lamp circuit short to ground detected. Lamp may be illuminated continuously; fault stored in instrument cluster/BCM memory.
Repair difficulty: Medium
Diagnostic time: 0.5-3 hours
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Code
B1378
FIAT
B — Body
Oil change warning lamp circuit short to ground
Views:
UK: 3
EN: 4
RU: 4
AI status
Completed
Completed
100%
Causes
- Damaged wiring insulation with conductor contacting chassis ground
- Corroded or water-damaged lamp socket or connector
- Shorted lamp bulb or LED module
- Poor/loose ground or additional aftermarket grounding/modification
- Faulty instrument cluster or body control module (mis-driving the circuit)
- Pinched harness where it passes through body panels or bulkheads
Symptoms
- Oil change or service-wrench/warning lamp illuminated when it should be off
- Unable to reset service interval or lamp remains lit after reset attempt
- Related instrument cluster lamp anomalies or intermittent lamp behavior
- Possible battery drain if short is permanent
- Stored B1378 and possibly related lamp circuit DTCs in module memory
What to check
- Retrieve DTCs and freeze-frame data with a diagnostic scanner; note ignition and engine conditions when fault set
- Visually inspect lamp socket, connector, and harness for damage, corrosion, or water ingress
- Inspect ground points and body harness routing for chafe or contact with sharp edges
- Disconnect the instrument cluster or lamp connector and see if the fault clears (to isolate wiring vs. module)
- Measure continuity between lamp feed and chassis ground with ignition off; and resistance of lamp circuit
- Back-probe lamp supply with ignition ON to verify voltage and switching behavior while commanding lamp on/off via scan tool if available
Signal parameters
- Expected: With ignition ON and lamp not commanded, lamp feed should be open circuit to ground (high resistance, e.g., >10 kΩ)
- Expected: When module commands lamp ON, the module provides a ground (low resistance path) or switches supply depending on design; verify OEM wiring diagram
- Short indication: continuous low resistance to ground (
- Voltage: lamp supply should be ~battery voltage (~11–14 V) at the feed terminal when power is present; signal to ground should only be present when commanded by module
Diagnostic algorithm
- Connect a scan tool, read and record DTCs and freeze frame. Confirm B1378 is current or historic.
- Verify symptom: is oil change lamp illuminated? Try servicing/reset procedure to see if lamp clears.
- Visually inspect lamp socket, cluster connector, harness routing and ground points for obvious damage, corrosion or water entry.
- With ignition OFF, disconnect the oil change lamp connector (or instrument cluster connector) and check if the DTC clears or changes after cycling ignition. If fault clears, problem is in wiring/lamp. If not, suspect module.
- Measure resistance between lamp feed and chassis ground (ignition OFF). A low resistance indicates a short to ground.
- With ignition ON, back-probe the lamp feed to check for battery voltage and observe behaviour while commanding the lamp ON/OFF via scan tool. Note if circuit is permanently grounded.
- Perform a wiggle/stress test along the harness while monitoring the circuit for intermittent shorts. Pay attention to bulkhead pass-throughs and areas where harness contacts metal.
- Isolate sections by unplugging intermediate connectors to localize short location. Repair any damaged wires, replace corroded connectors, or re-pin damaged terminals.
- If wiring and connectors check good, consider replacing or bench-testing the instrument cluster/BCM per OEM procedure.
- After repair, clear codes, perform functional test and road/test cycle to ensure the fault does not return.
Likely causes
- Wiring harness chafe in engine bay or dash harness where it rubs on metal
- Corrosion/water ingress at the lamp socket or cluster connector
- Failed lamp/LED inside the cluster causing internal short
- Connector pins pushed out or contacting ground at a mounting point
- Instrument cluster/BCM internal short (less common)
Fault status
Status
Oil change/service lamp circuit short to ground detected. Lamp may be illuminated continuously; fault stored in instrument cluster/BCM memory.
Repair difficulty: Medium
Diagnostic time: 0.5-3 hours
Similar codes
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Code
B1378
HUMMER
B — Body
Device Ignition 3 (ON) Circuit High (BCM)
Views:
UK: 3
EN: 8
RU: 10
AI status
Completed
Completed
100%
Causes
- Damaged wiring insulation with conductor contacting chassis ground
- Corroded or water-damaged lamp socket or connector
- Shorted lamp bulb or LED module
- Poor/loose ground or additional aftermarket grounding/modification
- Faulty instrument cluster or body control module (mis-driving the circuit)
- Pinched harness where it passes through body panels or bulkheads
Symptoms
- Oil change or service-wrench/warning lamp illuminated when it should be off
- Unable to reset service interval or lamp remains lit after reset attempt
- Related instrument cluster lamp anomalies or intermittent lamp behavior
- Possible battery drain if short is permanent
- Stored B1378 and possibly related lamp circuit DTCs in module memory
What to check
- Retrieve DTCs and freeze-frame data with a diagnostic scanner; note ignition and engine conditions when fault set
- Visually inspect lamp socket, connector, and harness for damage, corrosion, or water ingress
- Inspect ground points and body harness routing for chafe or contact with sharp edges
- Disconnect the instrument cluster or lamp connector and see if the fault clears (to isolate wiring vs. module)
- Measure continuity between lamp feed and chassis ground with ignition off; and resistance of lamp circuit
- Back-probe lamp supply with ignition ON to verify voltage and switching behavior while commanding lamp on/off via scan tool if available
Signal parameters
- Expected: With ignition ON and lamp not commanded, lamp feed should be open circuit to ground (high resistance, e.g., >10 kΩ)
- Expected: When module commands lamp ON, the module provides a ground (low resistance path) or switches supply depending on design; verify OEM wiring diagram
- Short indication: continuous low resistance to ground (
- Voltage: lamp supply should be ~battery voltage (~11–14 V) at the feed terminal when power is present; signal to ground should only be present when commanded by module
Diagnostic algorithm
- Connect a scan tool, read and record DTCs and freeze frame. Confirm B1378 is current or historic.
- Verify symptom: is oil change lamp illuminated? Try servicing/reset procedure to see if lamp clears.
- Visually inspect lamp socket, cluster connector, harness routing and ground points for obvious damage, corrosion or water entry.
- With ignition OFF, disconnect the oil change lamp connector (or instrument cluster connector) and check if the DTC clears or changes after cycling ignition. If fault clears, problem is in wiring/lamp. If not, suspect module.
- Measure resistance between lamp feed and chassis ground (ignition OFF). A low resistance indicates a short to ground.
- With ignition ON, back-probe the lamp feed to check for battery voltage and observe behaviour while commanding the lamp ON/OFF via scan tool. Note if circuit is permanently grounded.
- Perform a wiggle/stress test along the harness while monitoring the circuit for intermittent shorts. Pay attention to bulkhead pass-throughs and areas where harness contacts metal.
- Isolate sections by unplugging intermediate connectors to localize short location. Repair any damaged wires, replace corroded connectors, or re-pin damaged terminals.
- If wiring and connectors check good, consider replacing or bench-testing the instrument cluster/BCM per OEM procedure.
- After repair, clear codes, perform functional test and road/test cycle to ensure the fault does not return.
Likely causes
- Wiring harness chafe in engine bay or dash harness where it rubs on metal
- Corrosion/water ingress at the lamp socket or cluster connector
- Failed lamp/LED inside the cluster causing internal short
- Connector pins pushed out or contacting ground at a mounting point
- Instrument cluster/BCM internal short (less common)
Fault status
Status
Oil change/service lamp circuit short to ground detected. Lamp may be illuminated continuously; fault stored in instrument cluster/BCM memory.
Repair difficulty: Medium
Diagnostic time: 0.5-3 hours
Similar codes
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Code
B1378
Other
B — Body
Oil Change Lamp Circuit Short To Ground
Views:
UK: 11
EN: 26
RU: 18
AI status
Completed
Completed
100%
Causes
- Damaged wiring insulation with conductor contacting chassis ground
- Corroded or water-damaged lamp socket or connector
- Shorted lamp bulb or LED module
- Poor/loose ground or additional aftermarket grounding/modification
- Faulty instrument cluster or body control module (mis-driving the circuit)
- Pinched harness where it passes through body panels or bulkheads
Symptoms
- Oil change or service-wrench/warning lamp illuminated when it should be off
- Unable to reset service interval or lamp remains lit after reset attempt
- Related instrument cluster lamp anomalies or intermittent lamp behavior
- Possible battery drain if short is permanent
- Stored B1378 and possibly related lamp circuit DTCs in module memory
What to check
- Retrieve DTCs and freeze-frame data with a diagnostic scanner; note ignition and engine conditions when fault set
- Visually inspect lamp socket, connector, and harness for damage, corrosion, or water ingress
- Inspect ground points and body harness routing for chafe or contact with sharp edges
- Disconnect the instrument cluster or lamp connector and see if the fault clears (to isolate wiring vs. module)
- Measure continuity between lamp feed and chassis ground with ignition off; and resistance of lamp circuit
- Back-probe lamp supply with ignition ON to verify voltage and switching behavior while commanding lamp on/off via scan tool if available
Signal parameters
- Expected: With ignition ON and lamp not commanded, lamp feed should be open circuit to ground (high resistance, e.g., >10 kΩ)
- Expected: When module commands lamp ON, the module provides a ground (low resistance path) or switches supply depending on design; verify OEM wiring diagram
- Short indication: continuous low resistance to ground (
- Voltage: lamp supply should be ~battery voltage (~11–14 V) at the feed terminal when power is present; signal to ground should only be present when commanded by module
Diagnostic algorithm
- Connect a scan tool, read and record DTCs and freeze frame. Confirm B1378 is current or historic.
- Verify symptom: is oil change lamp illuminated? Try servicing/reset procedure to see if lamp clears.
- Visually inspect lamp socket, cluster connector, harness routing and ground points for obvious damage, corrosion or water entry.
- With ignition OFF, disconnect the oil change lamp connector (or instrument cluster connector) and check if the DTC clears or changes after cycling ignition. If fault clears, problem is in wiring/lamp. If not, suspect module.
- Measure resistance between lamp feed and chassis ground (ignition OFF). A low resistance indicates a short to ground.
- With ignition ON, back-probe the lamp feed to check for battery voltage and observe behaviour while commanding the lamp ON/OFF via scan tool. Note if circuit is permanently grounded.
- Perform a wiggle/stress test along the harness while monitoring the circuit for intermittent shorts. Pay attention to bulkhead pass-throughs and areas where harness contacts metal.
- Isolate sections by unplugging intermediate connectors to localize short location. Repair any damaged wires, replace corroded connectors, or re-pin damaged terminals.
- If wiring and connectors check good, consider replacing or bench-testing the instrument cluster/BCM per OEM procedure.
- After repair, clear codes, perform functional test and road/test cycle to ensure the fault does not return.
Likely causes
- Wiring harness chafe in engine bay or dash harness where it rubs on metal
- Corrosion/water ingress at the lamp socket or cluster connector
- Failed lamp/LED inside the cluster causing internal short
- Connector pins pushed out or contacting ground at a mounting point
- Instrument cluster/BCM internal short (less common)
Fault status
Status
Oil change/service lamp circuit short to ground detected. Lamp may be illuminated continuously; fault stored in instrument cluster/BCM memory.
Repair difficulty: Medium
Diagnostic time: 0.5-3 hours
Similar codes
Workshop Manuals
Available brands with manuals
1
LAND ROVER 1
Land Rover Defender Workshop Manual Supplement & Body Repair Manual (1999 & 2002 MY)
Workshop ManualWorkshop Manual Supplement and Body Repair Manual for the Land Rover Defender. Includes general specifications, maintenance schedules, tuning data and step‑by‑step repair procedures for engine, transmission, suspension, brakes, electrical and body repairs. Covers Defender models from 1999 and 2002 model years.
Key sections:
Buy - 01 - INTRODUCTION
- - Introduction
- - Dimensions
- - References
- - Repairs and replacements
- - Poisonous substances
- - Fuel handling precautions
- - Synthetic rubber
- - Recommended sealants
- - Used engine oil precautions
- - Accessories and conversions
- - Wheels and tyres
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