Code
P1900
FORD
P — Powertrain
Output Shaft Speed (OSS) Circuit Intermittent Malfunction
Views:
UK: 34
EN: 65
RU: 54
AI status
Completed
Completed
100%
Causes
- Damaged, corroded or loose OSS connector or wiring (intermittent open/short)
- Faulty OSS (output shaft speed) sensor
- Poor or intermittent ground at sensor or PCM
- Intermittent short to battery or chassis ground in harness
- Contaminated sensor or magnetic pickup (debris/metal on tone ring)
- Intermittent internal transmission fault affecting the pickup
Symptoms
- Malfunction Indicator Lamp (MIL/CEL) illuminated (intermittent)
- Erratic or harsh shifting, unexpected torque converter lockup/unlock behavior
- Transmission slips or goes into fail-safe/limp mode under certain conditions
- Driveability complaints related to shift quality or hesitation
- Possible incorrect/unstable speed readings in transmission control data (may not affect dash speed if separate VSS)
What to check
- Read stored DTC(s) and freeze-frame data with a capable scan tool; note conditions when code set
- Capture live OSS data (signal, frequency, and vehicle speed) while reproducing problem
- Compare OSS signal to wheel speed or input speed sensors to check plausibility
- Visually inspect OSS connector and wiring for damage, corrosion, pin push-out, or water entrainment
- Wiggle harness and connectors while watching live data to try to reproduce intermittent behavior
- Backprobe sensor connector and check for proper reference power, ground, and signal with engine running or during transmission input (as appropriate)
Signal parameters
- Sensor type may be VR (variable reluctance) or Hall-effect depending on model — confirm with vehicle wiring diagram
- VR sensor: AC voltage waveform that increases with shaft speed; amplitude and frequency rise with RPM
- Hall-effect sensor: square wave 0–5V (or switch between ground and reference) with increasing frequency as speed increases
- Expected behavior: clean, consistent pulses whose frequency tracks vehicle speed; intermittent loss, excessive noise, or irregular amplitude indicates fault
- If available, compare OSS frequency to wheel-speed or gearbox input frequency for consistency
Diagnostic algorithm
- Retrieve all related codes and freeze-frame/snapshot data; note engine/transmission operating conditions when code occurred.
- Perform a visual inspection of transmission harness, connectors, and OSS sensor mounting; repair any obvious damage.
- With a scan tool, monitor OSS PID and other speed-related PIDs during road test or transmission dynamometer test to try to reproduce the intermittent event.
- Backprobe the sensor connector and check for proper reference voltage (if Hall-type), ground continuity, and signal presence while rotating the output shaft or during road test. Use an oscilloscope where possible to capture intermittent anomalies.
- Wiggle the harness and connectors while watching live data to locate an intermittent wiring/connector fault.
- Inspect tone ring or reluctor wheel for missing/damaged teeth, heavy contamination, or debris that could intermittently affect the sensor.
- Check continuity and resistance of sensor wiring to the PCM; repair any chafing, shorts to ground/battery, or high resistance connections.
- If wiring and connectors test good and the tone ring is intact, bench-test or replace the OSS sensor with a known-good unit and re-test.
- If a new sensor does not resolve intermittent faults, consult vehicle-specific wiring diagrams and consider PCM or transmission control module testing or reflash as a last step.
- Clear codes and perform a verification road test under the conditions that originally set the code.
Likely causes
- Wiring harness abrasion where it flexes (intermittent contact)
- Corroded connector pin or water intrusion at transmission harness connector
- Sensor failing under temperature/vibration but passes static bench tests
- Broken or damaged tone ring teeth or debris on tone wheel causing intermittent pulses
Fault status
Status
Intermittent malfunction detected in the Output Shaft Speed (OSS) circuit. Signal dropouts, noise, or sporadic pulses were observed; fault was not continuously present.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 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