The P0725: Engine Speed Input Circuit code indicates an issue in the circuit that sends the engine speed signal to the vehicle’s computer systems. This signal is vital for proper engine and transmission operation, as it helps regulate various functions like shifting gears in an automatic transmission. A fault in this system can lead to problems with how the vehicle drives, including stalling or uneven acceleration.
P0725 quick overview
| Meaning | P0725: Engine Speed Input Circuit |
| Is it serious? | This code can be serious as it affects the vehicle’s ability to gauge engine speed, which can lead to stalling or erratic driving behavior. |
| Possible causes | – Faulty Crankshaft Position (CKP) sensor – Wiring issues related to the CKP sensor – Faults within the Transmission Control Module (TCM) – Poor electrical connections in the engine speed sensor circuit – ECM issues affecting communication with the TCM |
| How to diagnose? | Inspect CKP Sensor: Check the condition and connection of the Crankshaft Position sensor. Review Wiring: Examine the wiring to the CKP sensor for damages or disconnections. Check TCM Data: Analyze Transmission Control Module data for discrepancies in engine speed readings. Evaluate Electrical Connections: Ensure all related electrical connections are secure and corrosion-free. Confirm Sensor Functionality: Test the CKP sensor and related components to verify proper functionality. |
P0725 Meaning
Code P0725 means there’s a problem with the part of your car that tells the computer how fast the engine is running. This can cause the car to stall or not drive smoothly because the computer needs this information to control things like shifting gears. It’s important to get this fixed to avoid driving issues. The usual steps to sort this out include checking the sensor that measures engine speed, looking at the wiring, and making sure the computer systems that use this information are working right.
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How to fix P0725 – learn from mechanics
I looked into P0725 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.
Case #1: Mazda
Vehicle Information: 1999 Mazda Millenia 2.3L
Issue + Repair History:
- Car arrived with low power and surging idle.
- Vacuum lines were crossed, corrections made but issues persisted.
- Disconnecting ABV improved power, but idle still surged, and car would stall while driving.
- Vacuum at MAP sensor was absent at idle.
- Supercharger had been replaced previously with a new Mazda part.
Computer Codes & Descriptions:
- P0725: Engine Speed Sensor Malfunction
Suggestions to Fix Issue:
- Perform diagnostic test on P0725 and clear codes to see if it resets.
- Check hose at MAP sensor and throttle body base for vacuum supply issues.
- Inspect areas providing vacuum sources for possible blockage.
Final Fix:
- Stalling problem was due to a bad airflow sensor.
- After replacing airflow sensor, surging idle persisted.
- Further testing revealed rust in the fuel rail.
- Owner declined further repairs.
Case #2: Nissan
Vehicle Information: 1996 Nissan Maxima SE 3.0L
Issue + Repair History:
- Vehicle dies when put in gear.
- Scanner shows code P0725 and indicates the car is in third gear.
- Operates in forward and reverse on the lift, but dies immediately on the ground.
- New front pump and converter were installed, after which the vehicle got stuck in 3rd gear.
- Transmission was rechecked; no issues found with the new pump.
Other Test Results:
- Scanner code: P0725
Suggestions to Fix Issue:
- Check if the tachometer and speedometer are working correctly.
- Investigate if the torque converter is stuck in the locked-up mode.
- Check the TCC (Torque Converter Clutch) solenoid to ensure it’s not causing lockup.
- Consider the possibility of a bad electrical sensor.
Final Fix:
- Found that a bushing was installed incorrectly.
- Replacing the bushing fixed the car’s issue.
Case #3: Dodge
Vehicle Information: 1999 Dodge Stratus 2.4L
Issue + Repair History:
- Code P0725 appeared, indicating an engine speed sensor signal issue.
- Shop replaced the transmission computer, but the code reappeared after warming up.
- Engine RPM goes to zero in the transmission computer after warm-up, despite good CKP signal to both ECM and TCM.
- ECM does not set a code and shows RPM when the transmission does not.
- Voltage drop on TCM ground is good.
Related Repair History:
- Transmission computer replaced.
Suggestions to Fix Issue:
- Check connector pins at TCM for full contact.
- Set the pinion factor, if not already done.
- Unplug other modules one by one to see if transmission data is affected.
- Consider input speed sensor as a possible cause.
Final Fix:
- The issue was with the voltage amplitude of the CKP sensor signal.
- Signal was around 4 volts, not sufficient enough; ideally, it should be 5 volts.
- Cutting the signal wire from the ECM showed the supply was okay.
- Replacing the CKP sensor resolved the issue, as it was dropping voltage to a constant 4 volts.
Case #4: Volkswagen
Vehicle Information: 2001 Volkswagen EuroVan GLS 2.8L
Issue + Repair History:
- Vehicle wouldn’t start after another shop installed a new battery.
- No check engine light, but PCM communication seems fine.
- All fuses checked and appeared okay.
Related Repair History:
- New battery installed by another shop.
Computer Codes & Descriptions:
- P0725: Engine Speed Input Circuit Malfunction
Suggestions to Fix Issue:
- Check for potential anti-theft system activation due to battery replacement.
- Visually inspect the area around the battery for any disconnected connectors or disturbed wiring.
- Clear the code and attempt to crank the vehicle.
- Disconnect the speed input sensor after clearing codes and test the vehicle.
- Consider PCM reprogramming, especially for idle parameters, after battery disconnection.
Final Fix:
- The issue was resolved by replacing the PCM.
- The replacement PCM cost was nearly $600.
Case #5: Mitubishi
Vehicle Information: 2008 Mitsubishi Lancer GTS 2.0L
Issue + Repair History:
- Vehicle experienced stalling and hesitation.
- Diagnosed with code P0725.
- Crank position sensor replaced, but check engine light returned with the same code.
Related Repair History:
- Replaced Crankshaft Position (CKP) sensor.
Computer Codes & Descriptions:
- P0725: CKP Sensor
Other Test Results:
- Same code resurfaced after CKP sensor replacement.
Suggestions to Fix Issue:
- Check if TCM receives engine speed signal correctly from ECM and compares it with the transmission’s input and output sensors.
- Review TCM scan data for engine speed signal.
- Check for shorts or open circuits in CKP sensor wiring.
- Inspect for a possible communication error between ECM and TCM.
- Verify the input speed sensor, as P0725 is related to input turbine speed.
Final Fix:
- The issue was resolved by repairing a bent pin in the CKP sensor that was not making proper contact.
- Straightening the pin corrected the problem.
How to diagnose P0725
I made you an overview of solving this DTC, based on all the advice that was suggested by certified mechanics to address this issue in previously mentioned service cases.
| Advice | Brief Description of Diagnostic Step |
|---|---|
| Check CKP Sensor Wiring | Inspect the wiring of the Crankshaft Position (CKP) sensor for shorts, open circuits, or poor electrical connections. |
| Review TCM Data | Examine Transmission Control Module (TCM) scan data to compare engine speed signal with transmission input and output sensors. |
| Inspect Electrical Connections | Ensure all electrical connections, especially to the CKP sensor, are secure and free of corrosion. |
| Evaluate ECM and TCM Communication | Check for possible communication errors between the Engine Control Module (ECM) and the Transmission Control Module (TCM). |
| Confirm Correct Sensor Replacement | Verify that the correct sensor, related to the P0725 code, has been replaced and is functioning properly. |
| Test Sensor Functionality | Perform tests on the relevant sensors, such as input speed sensor or CKP sensor, to ensure proper operation. |
Car Diagnostics Training
- Car Electrical basics
- OBD-II scanner basics
- How to use an OBD reader
- Introduction to a Bi-directional Scan tool
- OBD scanner buyer’s guide + discounts
Hi, I am Juraj “Yuri” Lukacko. I got frustrated by unhelpful and scammy mechanics, so I decided to learn everything about car diagnostics myself. I test dozens of new car diagnostic tools every month along with learning new strategies to fix and customize cars. About Juraj Lukacko (Yuri)