P0718
Input/Turbine Speed Sensor "A" Circuit Intermittent
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The P0718 code indicates that the input/turbine speed sensor signal is cutting in and out intermittently. The TCM has detected momentary dropouts or spikes in the signal that aren't consistent enough to set a hard fault code like P0717, but are frequent enough to flag an intermittent problem. This is often the most challenging of the input speed sensor codes to diagnose because the fault may not be present during testing.
Driving symptoms will mirror the intermittent nature of the fault. You may have several trips with perfectly normal shifting, followed by a drive where the transmission shifts harshly, slips, or briefly enters limp mode before returning to normal. The check engine light may illuminate and then clear itself. These come-and-go symptoms are the hallmark of an intermittent electrical connection issue.
To diagnose this code, start with a careful physical inspection of the sensor connector and wiring harness. Look for loose pins, corroded terminals, or wires that may have been nicked or chafed by nearby components. Perform a wiggle test while monitoring the sensor signal on a scan tool. If the wiring appears sound, check the transmission fluid for metallic contamination that could periodically cling to the sensor's magnetic tip. Don't ignore this code — intermittent faults tend to become permanent over time, and the resulting uncontrolled shifting can damage the transmission.
Severity
Symptoms
- •Occasional harsh or delayed shifts
- •Transmission slips intermittently
- •Sporadic limp mode that resolves after restart
- •Momentary speedometer fluctuations
- •Check engine light that may come and go
- •Unpredictable torque converter shudder
Likely Causes
A connector that isn't fully seated or a wire with a partial break can maintain contact under some conditions but lose it during vibration, thermal expansion, or when going over bumps.
The sensor may work fine when cold but fail as it heats up, or it may produce dropouts when the transmission reaches certain speeds due to internal component degradation.
Metal particles in the transmission fluid may occasionally accumulate on the sensor tip and then fall away, causing sporadic signal interruptions that the TCM flags as intermittent.
A chipped or slightly damaged tooth on the reluctor ring will cause a brief signal dropout once per revolution at certain speeds, which the TCM may flag intermittently.
Estimated Cost
Professional Repair
Includes parts + labor
Common Fixes
- Inspect and reseat the speed sensor connector
- Replace the input/turbine speed sensor
- Repair or replace damaged wiring in the sensor circuit
- Change transmission fluid and filter to remove debris