By iCarsoft Official Store Technical Team, Automotive Diagnostics Editors · Updated September 21, 2026 · OEM technical references checked
Quick Answer
P0873 concerns Transmission Fluid Pressure Sensor/Switch C Circuit High. The code does not prove the transmission has a universal high fluid pressure, the pressure sensor is failed, or Switch C has the same location on every vehicle. Save the event, identify the exact architecture and test the physical and electrical paths before selecting a repair.
What Does the P0873 Code Mean?
The P0873 code means Transmission Fluid Pressure Sensor/Switch C Circuit High. It names a monitored result, not a guaranteed failed part. The reporting module, suffix and companion faults determine the relevant test branch.
Transmission pressure monitoring may use switches, analog sensors, multiplexed data or a valve-body module. P0873 describes a high signal classification for the OEM-defined C channel, not a direct hydraulic pressure measurement.
A reported transmission fluid pressure sensor or switch C signal value and the physical system response are separate evidence. A scanner display alone does not prove the component or wiring is healthy.
The standardized description is Transmission Fluid Pressure Sensor/Switch C Circuit High. The C label and test port are VIN-specific; identify the wiring diagram and hydraulic procedure before naming a component.
Generic DTC wording is a starting point; confirm the complete OEM description, enable conditions and VIN-specific procedure.
Read the stored wording exactly as the vehicle reports it. A short generic label can hide a manufacturer suffix, a circuit-direction detail, a bank or sensor identifier, or a setup condition that changes the first test. Save that wording before clearing the record so the diagnostic path can be repeated if the fault returns.
Separate P0873 from adjacent fault families
| Code | General description | Key distinction |
|---|---|---|
| P0873 | Transmission Fluid Pressure Sensor/Switch C Circuit High | Use the full OEM wording, status and companion faults before choosing a test path. |
| P0871 | Code guide | Related monitor family; confirm its separate fault criteria before combining repairs. |
| P0872 | Code guide | Related monitor family; confirm its separate fault criteria before combining repairs. |
| P0874 | Code guide | Related monitor family; confirm its separate fault criteria before combining repairs. |
Record the complete P0873 description. The suffix, reporting module and companion faults can change the diagnostic path. Use the manufacturer's full wording and test procedure for the exact vehicle.
P0873 Symptoms and Likely Causes
P0873 symptoms depend on fault status and the fallback strategy. Record what the driver and modules reported. A symptom list is not a parts list.
Look for patterns rather than isolated clues. A current fault with matching freeze-frame data deserves a different priority than an old history fault found during unrelated service. Companion codes can point to a shared feed, ground, connector, fluid state, mechanical path or controller condition, but they still need the same evidence-based separation.
Save gear, pressure, temperature and companion solenoid faults.
Do not continue a road test when engagement is unsafe or unpredictable.
Record the selected gear and conditions before clearing.
An electrical monitor can set before hydraulic performance changes.
Practical cause-checking order
- Identify the exact system: Map Sensor or Switch C, its connector and the reporting module for the exact transmission.
- Connector and circuit evidence: Inspect fluid intrusion, terminal tension, reference, ground, signal and shared harness paths.
- Physical or fluid evidence: Test the circuit in the required key-on or running state and separate electrical high from a real hydraulic reading.
- Command and response evidence: Compare supported pressure data with an approved mechanical pressure test and shift symptoms.
- Controller or service action: Consider valve-body, controller or calibration work only after the circuit and hydraulic evidence agree.
Did P0873 appear after recent transmission, valve-body, fluid, battery, solenoid or harness work? Recheck the documented connections, parts and setup steps affected by that work. Record battery and software history; a post-repair code does not prove the new part is defective.
How Serious Is P0873, and Can You Drive?
P0873 alone cannot establish a safe driving distance. If operation is normal, follow the owner's manual and arrange prompt diagnosis. Stop for the transmission slips, bangs into gear, will not select a safe gear, overheats, leaks fluid or causes loss of propulsion.
Record temperature, load, speed, start state and recent service. Do not reproduce a severe symptom on public roads; another warning can make the situation more urgent. If the vehicle enters a reduced-power strategy, develops abnormal noise, leaks fluid, overheats or shows a red stop warning, the safety condition overrides any plan to complete a drive cycle.
Stop and arrange a tow if the transmission slips, bangs into gear, will not select a safe gear, overheats, leaks fluid or causes loss of propulsion.
Use the exact OEM safety procedure for transmission fluid pressure sensor or switch C signal. Do not probe energized high-current, fuel, refrigerant or high-voltage circuits, and keep clear of hot parts, fans and moving mechanisms.
How to Diagnose P0873 in the Right Order
-
Preserve P0873 data
Save current, pending and history faults, freeze frame, gear, load, fluid temperature and recent service. Do not clear before recording the original event.
-
Map pressure Sensor/Switch C
Use the VIN transmission diagram to identify C, its connector, reference, ground, signal and any valve-body module.
-
Inspect the transmission circuit safely
Secure the vehicle and allow hot components to cool. Inspect connector, fluid contamination, harness routing and recent work without opening a pressurized circuit.
-
Test the high-signal branch
Follow the OEM circuit and loaded-signal tests with the correct power state. Do not apply power to an unidentified pressure circuit.
-
Separate electrical and hydraulic evidence
Compare supported scan pressure with the manufacturer-approved mechanical gauge or switch test. A high PID is not a substitute for physical pressure evidence.
-
Repair and verify shift quality
Repair the proven connector, wire, sensor, switch or hydraulic branch; perform required fluid, adaptation and verification procedures, then recheck faults and shifts.
Specifications are vehicle-specific. Use the exact VIN specifications, approved test points and required operating state. No generic value or drive cycle can replace the applicable procedure. Manufacturer examples here do not establish specifications for other applications.
P0873 Repairs and Typical Costs
The correct P0873 repair follows the failed test. Wiring, a physical repair, a proven component, software and controller work are different outcomes. Do not replace an assembly from the generic code alone.
Recheck installation and required setup after repair. Repair the demonstrated branch first, then complete the required setup, clearing and monitor verification procedure.
A useful estimate should name the failed branch, not just the code. Ask whether the shop found an open, short, biased signal, missing supply, poor ground, mechanical restriction, fluid condition, calibration requirement or module fault. That wording makes the recommendation auditable and protects against replacing several unrelated parts after one stored DTC.
When the failed branch is still uncertain, pay for diagnosis before authorizing parts. A careful proof step is usually less disruptive than repeating repairs after the same monitor sets again.
| Possible path | Current US estimate |
|---|---|
| Restore connector, reference, ground, signal or shared harness evidence | VIN-specific quote |
| Correct fluid level, contamination or valve-body issue supported by testing | VIN-specific quote |
| Replace Sensor/Switch C only after its exact circuit and pressure test fails | VIN-specific quote |
| Complete transmission adaptation or controller action only when specified | VIN-specific quote |
These are alternative repair paths, not prices to add together. Request a VIN-specific quote separating diagnosis, parts, labor, fluids, taxes, required setup and verification. Ask which failed test supports the proposed repair and whether warranty coverage applies.
Using iCarsoft CR Ultra P for P0873
On a supported vehicle, iCarsoft CR Ultra P can retrieve accessible module faults, save available freeze frame, display ECU-provided live data and create a diagnostic report. For P0873, preserve the original evidence and compare related modules before clearing an erasable record.
Use the report as a record of what the controller knew at the time. It helps compare code status, freeze-frame conditions and available PIDs before and after repair. It does not replace the wiring diagram, service procedure, safe access instructions or physical measurement required to prove the failed branch.
Preserve the transmission fluid pressure sensor or switch C signal evidence
iCarsoft CR Ultra P
Review supported codes and relevant live data together. Confirm the exact VIN, controller access, PIDs and any requested active test with iCarsoft before purchase; generic product capabilities do not guarantee a P0873-specific function.
Check current CR Ultra P price and availabilityCheck CR Ultra P compatibility by VINThe official product page describes supported vehicle diagnostics, available live data and diagnostic reports; exact module access and functions depend on the vehicle, ECU and software. Confirm the requested function by VIN before purchase. Follow OEM prerequisites and stop for abnormal operation.
Know the measurement boundary. Scan data describes ECU-provided information; it does not directly prove the physical condition of the transmission fluid pressure sensor or switch C signal. Use a high-impedance meter, loaded-circuit tools, a scan tool with supported transmission data and the manufacturer-approved pressure gauge where required, and compare reported values with the relevant measured evidence.
Verify the P0873 Repair
After repair, verify connectors, harness clearance, setup and controller supply. Save post-repair findings, then clear only erasable records through the approved procedure. Battery disconnection is not a repair.
Run the manufacturer's applicable verification conditions in a safe workshop or route. Compare the original operating state with current data for the transmission fluid pressure sensor or switch C signal, and check current and pending faults in related modules. One clean start or idle period does not prove that every conditional monitor has completed.
Document what changed between the first scan and the verification scan. Useful notes include module status, current versus history state, freeze-frame differences, whether the same enabling conditions returned, and whether a relearn or service function was accepted. Preserve the original diagnostic fault order. This record helps separate an incomplete monitor from a repair that failed under the same conditions.
If P0873 returns, compare its suffix, status, failure order and operating conditions with the saved baseline before replacing another part. Revisit the failed branch and inspect anything disturbed. Keep mechanical repair, monitor completion, readiness and local inspection eligibility as separate outcomes.
A permanent P0873 can remain immediately after a successful repair. If stored as a permanent DTC, it cannot be erased by a scan tool or battery disconnect. The vehicle must complete the applicable successful monitor verification.
Related Transmission Fluid Pressure Sensor Or Switch C Signal Code Guides
Use related-code pages to compare monitor families, not to merge repairs. A nearby code can share a component, circuit, fluid path or operating condition, but its diagnostic conclusion still depends on its own status, suffix and test evidence.
P0873 Frequently Asked Questions
Does P0873 prove the named component has failed?
No. P0873 describes transmission fluid pressure sensor/switch c circuit high, not a confirmed part. It also does not prove the transmission has a universal high fluid pressure, the pressure sensor is failed, or Switch C has the same location on every vehicle. Follow the exact OEM test sequence.
What should I check first for P0873?
Save every module's codes and freeze frame before clearing. Confirm the full definition, suffix and VIN architecture. Then inspect recent transmission, valve-body, fluid, battery, solenoid or harness work, connectors and shared supplies. Those facts determine whether the next test needs a high-impedance meter, loaded-circuit tools, a scan tool with supported transmission data and the manufacturer-approved pressure gauge or a manufacturer-specific functional procedure.
Can I drive with the P0873 code?
P0873 alone cannot establish a safe driving distance. If operation is normal, follow the owner's manual and arrange prompt diagnosis. Stop for the transmission slips, bangs into gear, will not select a safe gear, overheats, leaks fluid or causes loss of propulsion.
Why did P0873 return after a part was replaced?
If P0873 returns, compare status, companion codes and operating conditions with the saved baseline before replacing another part.
What should a P0873 repair estimate include?
Ask for the failed-test evidence and a VIN-specific breakdown of diagnosis, parts, labor, taxes, required setup and verification. A code alone cannot establish the repair price.
Can CR Ultra P diagnose and clear P0873?
On a supported vehicle, CR Ultra P can organize available faults, freeze frame, live data and reports, and can clear erasable records after repair. Confirm exact ECU coverage. It cannot force-clear a permanent DTC or replace physical measurements for the transmission fluid pressure sensor or switch C signal.
The iCarsoft Official Store Technical Team maintains the store's fault-code library. This guide organizes published manufacturer evidence and verified product information; it does not document a hands-on test of a particular vehicle or claim an individual engineer's review.
Technical and cost references
- SAE J2012 DTC terminology. The standardized C-channel label does not define the physical location or hydraulic specification.
- California Bureau of Automotive Repair — OBD test reference. A cleared transmission DTC is not proof that the monitored fault is resolved.
- California Bureau of Automotive Repair — On-Board Diagnostic Test Reference. Permanent DTCs are removed by the vehicle after applicable verification, not by a scan-tool erase command.
Product information: Official iCarsoft CR Ultra P page.
Editorial note: General diagnostic education, not a substitute for the owner's manual, current VIN-specific service information or professional inspection. Test limits, procedures, coverage and costs vary. Related articles provide context; apply only the specifications and repair procedures that match the vehicle. No universal failure rate, repair price or outcome is implied.
