Code
P0794
Generic
P — Powertrain
Intermediate Shaft Speed Sensor A Circuit Intermittent
Views:
UK: 13
EN: 17
RU: 18
AI status
Completed
Completed
100%
Causes
- Damaged, chafed, pinched or corroded wiring harness to the intermediate shaft speed sensor
- Loose, corroded or poorly seated sensor connector or terminals
- Faulty intermediate shaft speed sensor (hall-effect or variable-reluctance)
- Debris, metal shavings, or incorrect air gap between sensor and reluctor/target wheel
- Intermittent short to battery or ground in the sensor circuit (including chafed insulation contacting chassis or other conductors)
- Poor ground or power supply to the sensor
Symptoms
- Malfunction Indicator Lamp (MIL) or transmission fault lamp illuminated
- Erratic shifting, harsh or late shifts, or transmission slipping
- Possible limp-in (failure) mode reducing shift availability and engine torque
- Intermittent or inconsistent speed reading from intermediate shaft on scan tool
- Stored freeze-frame and intermittent DTC history entries
- Possible transmission vibration or unusual noise if sensor/reluctor contact is present
What to check
- Retrieve freeze frame, full DTC history and related transmission codes with a scan tool
- Record live data for intermediate shaft speed while key on, cranking, and running; monitor for dropouts or erratic values
- Perform a visual inspection of sensor, connector, and harness (look for damage, chafing, corrosion, loose mounting)
- Wiggle-test harness and connector while observing live data to try to reproduce the intermittent behavior
- Backprobe sensor connector with key on / engine off to verify reference voltage, ground, and expected resting voltage levels
- With engine running (or while turning the shaft as applicable) check the sensor waveform with an oscilloscope or appropriate scope-capable scan tool
Signal parameters
- Signal type depends on sensor design: hall-effect sensors typically produce a switched or PWM-like voltage referenced to 5 V (common resting/low-to-high swing ~0.5–4.5 V)
- Variable reluctance (VR) sensors produce an AC voltage whose amplitude increases with shaft speed (small AC mV at idle rising to volts at higher RPM)
- Expected behavior: clean, consistent pulses proportional to shaft speed with no dropouts, noise spikes, or irregular amplitude
- Frequency/pulse rate should scale smoothly with engine/transmission speed; sudden gaps, missing pulses, or intermittent polarity/voltage drops indicate a circuit problem
- No sustained short to battery (constant high) or to ground (constant low) under normal running conditions
Diagnostic algorithm
- Confirm DTC and record freeze-frame and related codes. Check for multiple occurrences and note when (idle, driving, shift events).
- Visual inspection: trace harness from sensor to module, inspect connector for corrosion, pins pushed out, debris, or damage. Check sensor mounting and reluctor condition. Repair obvious physical issues.
- With ignition ON, backprobe connector: verify reference voltage (if applicable), ground continuity, and resting signal level. Compare to service data for sensor type. Repair connector/power/ground faults.
- With engine cranking or running, monitor live data for intermediate shaft speed and wiggle the harness/connector to try to reproduce the intermittent fault. Use data logger if needed.
- Capture waveform with oscilloscope while turning shaft/engine running: look for clean pulses, consistent amplitude and timing. If waveform is noisy, missing pulses, or drops out, suspect wiring or sensor.
- Measure sensor resistance (for VR type) and compare to specifications; check for open or intermittent resistance. Check for short to power or ground.
- If wiring and connector test good, substitute known-good sensor or bench-test replacement if available. Re-test for fault. If intermittent persists, isolate and repair wiring (splice, shield, or replace harness) or replace sensor.
- After repair, clear codes and perform road test and data logging over multiple drive cycles to verify no recurrence. Consider replacing connector or protecting harness from heat/vibration where failures were found.
Likely causes
- Wire harness damaged at flex points, near transmission bellhousing, or where routed over suspension components
- Connector corrosion or bent pins allowing intermittent contact under vibration
- Sensor internal failure causing intermittent open or noisy output
- Reluctor/target wheel damaged, loose, or contaminated altering the sensor signal
- Intermittent short to power/ground when harness is flexed
- Poor ground at transmission case or chassis ground strap
Fault status
Status
Intermittent signal detected on Intermediate Shaft Speed Sensor A circuit — momentary loss, noise, or unexpected voltage/waveform variation recorded; code set and MIL may be illuminated.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
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Code
P0794
LAND ROVER
P — Powertrain
Intermediate circuit of the axle speed sensor
Views:
UK: 3
EN: 10
RU: 6
AI status
Completed
Completed
100%
Causes
- Damaged, chafed, pinched or corroded wiring harness to the intermediate shaft speed sensor
- Loose, corroded or poorly seated sensor connector or terminals
- Faulty intermediate shaft speed sensor (hall-effect or variable-reluctance)
- Debris, metal shavings, or incorrect air gap between sensor and reluctor/target wheel
- Intermittent short to battery or ground in the sensor circuit (including chafed insulation contacting chassis or other conductors)
- Poor ground or power supply to the sensor
Symptoms
- Malfunction Indicator Lamp (MIL) or transmission fault lamp illuminated
- Erratic shifting, harsh or late shifts, or transmission slipping
- Possible limp-in (failure) mode reducing shift availability and engine torque
- Intermittent or inconsistent speed reading from intermediate shaft on scan tool
- Stored freeze-frame and intermittent DTC history entries
- Possible transmission vibration or unusual noise if sensor/reluctor contact is present
What to check
- Retrieve freeze frame, full DTC history and related transmission codes with a scan tool
- Record live data for intermediate shaft speed while key on, cranking, and running; monitor for dropouts or erratic values
- Perform a visual inspection of sensor, connector, and harness (look for damage, chafing, corrosion, loose mounting)
- Wiggle-test harness and connector while observing live data to try to reproduce the intermittent behavior
- Backprobe sensor connector with key on / engine off to verify reference voltage, ground, and expected resting voltage levels
- With engine running (or while turning the shaft as applicable) check the sensor waveform with an oscilloscope or appropriate scope-capable scan tool
Signal parameters
- Signal type depends on sensor design: hall-effect sensors typically produce a switched or PWM-like voltage referenced to 5 V (common resting/low-to-high swing ~0.5–4.5 V)
- Variable reluctance (VR) sensors produce an AC voltage whose amplitude increases with shaft speed (small AC mV at idle rising to volts at higher RPM)
- Expected behavior: clean, consistent pulses proportional to shaft speed with no dropouts, noise spikes, or irregular amplitude
- Frequency/pulse rate should scale smoothly with engine/transmission speed; sudden gaps, missing pulses, or intermittent polarity/voltage drops indicate a circuit problem
- No sustained short to battery (constant high) or to ground (constant low) under normal running conditions
Diagnostic algorithm
- Confirm DTC and record freeze-frame and related codes. Check for multiple occurrences and note when (idle, driving, shift events).
- Visual inspection: trace harness from sensor to module, inspect connector for corrosion, pins pushed out, debris, or damage. Check sensor mounting and reluctor condition. Repair obvious physical issues.
- With ignition ON, backprobe connector: verify reference voltage (if applicable), ground continuity, and resting signal level. Compare to service data for sensor type. Repair connector/power/ground faults.
- With engine cranking or running, monitor live data for intermediate shaft speed and wiggle the harness/connector to try to reproduce the intermittent fault. Use data logger if needed.
- Capture waveform with oscilloscope while turning shaft/engine running: look for clean pulses, consistent amplitude and timing. If waveform is noisy, missing pulses, or drops out, suspect wiring or sensor.
- Measure sensor resistance (for VR type) and compare to specifications; check for open or intermittent resistance. Check for short to power or ground.
- If wiring and connector test good, substitute known-good sensor or bench-test replacement if available. Re-test for fault. If intermittent persists, isolate and repair wiring (splice, shield, or replace harness) or replace sensor.
- After repair, clear codes and perform road test and data logging over multiple drive cycles to verify no recurrence. Consider replacing connector or protecting harness from heat/vibration where failures were found.
Likely causes
- Wire harness damaged at flex points, near transmission bellhousing, or where routed over suspension components
- Connector corrosion or bent pins allowing intermittent contact under vibration
- Sensor internal failure causing intermittent open or noisy output
- Reluctor/target wheel damaged, loose, or contaminated altering the sensor signal
- Intermittent short to power/ground when harness is flexed
- Poor ground at transmission case or chassis ground strap
Fault status
Status
Intermittent signal detected on Intermediate Shaft Speed Sensor A circuit — momentary loss, noise, or unexpected voltage/waveform variation recorded; code set and MIL may be illuminated.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 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
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👎 Dislike
0
Send to email