What Does P1660 Mean?
The transmission control system has detected a failure in the Fuel Injection (FI) signal circuit A from the engine control module. This signal is used for transmission shift timing and torque management during gear changes.
Common Causes
35%
Wiring harness damage or open circuit between ECM and TCM
25%
Failed ECM output driver for FI signal circuit
20%
Failed transmission control module input circuit
15%
Corroded or damaged connectors at ECM or TCM
5%
Poor ground connection affecting signal integrity
Diagnostic Steps
1
Step 1: Verify communication between ECM and TCM using scan tool bidirectional controls
2
Step 2: Check FI signal circuit for continuity between ECM and TCM connectors
3
Step 3: Measure voltage on FI signal wire at TCM during engine operation (should pulse with injector signals)
4
Step 4: Inspect ECM and TCM connectors for corrosion, bent pins, or damaged terminals
5
Step 5: Monitor signal with oscilloscope to verify proper waveform amplitude and frequency
Estimated Repair Cost
$150 - $1,200
Parts + labor, varies by vehicle and location
The transmission control system has detected a failure in the Fuel Injection (FI) signal circuit A from the engine control module. This signal is used for transmission shift timing and torque management during gear changes.
The most common cause of P1660 (Automatic Transaxle FI Signal A Circuit Failure) is: Wiring harness damage or open circuit between ECM and TCM
Typical repair costs for P1660 range from $150 to $1,200, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Transmission may exhibit harsh shifts, delayed engagement, or improper shift timing due to lack of engine load information. May cause transmission damage if driven extensively.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1660 to identify the root cause.
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Quick Info
Category
Powertrain
System
Transmission Control System
Difficulty
Type
Manufacturer
Recommended Tools
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