What Does P0888 Mean?
The TCM has detected a general fault in the TCM power relay sense circuit. This circuit allows the TCM to verify that the power relay has actually engaged and is delivering voltage. If the sense circuit reports an unexpected condition, the TCM cannot confirm its own power supply status, which may trigger failsafe strategies.
Common Causes
30%
Open or damaged sense circuit wiring
25%
Failed TCM power relay (contacts not closing properly)
20%
Corroded connector at relay socket or TCM
15%
TCM internal sense circuit failure
10%
Blown fuse in sense circuit pathway
Diagnostic Steps
1
With key on and relay energized, verify that battery voltage is present on the relay output (sense) side — the TCM uses this to confirm relay engagement.
2
Check the sense circuit wire from the relay output pin to the TCM for continuity — an open will prevent the TCM from verifying power.
3
Test the relay by applying 12V directly to the coil and measuring contact closure resistance — worn contacts may not close reliably.
4
Inspect the relay socket and TCM connector for corrosion or spread terminals on the sense circuit pins.
5
If relay and wiring are good, the TCM sense input may be damaged — further diagnosis at a transmission specialist is recommended.
Estimated Repair Cost
$50 - $700
Parts + labor, varies by vehicle and location
The TCM has detected a general fault in the TCM power relay sense circuit. This circuit allows the TCM to verify that the power relay has actually engaged and is delivering voltage. If the sense circuit reports an unexpected condition, the TCM cannot confirm its own power supply status, which may tr...
The most common cause of P0888 (TCM Power Relay Sense Circuit) is: Open or damaged sense circuit wiring
Typical repair costs for P0888 range from $50 to $700, depending on the vehicle, location, and whether you do it yourself or go to a shop.
The TCM may intermittently enter failsafe mode if it cannot verify its own power status. Shifting may be unpredictable. Drive carefully to a repair facility.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0888 to identify the root cause.
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Quick Info
Category
Powertrain
System
Transmission Control Module Power Supply
Difficulty
Type
Generic (SAE)
Recommended Tools
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