Code
P1737
MITSUBISHI
P — Powertrain
Line pressure solenoid circuit
Views:
UK: 6
EN: 8
RU: 11
AI status
Completed
Completed
100%
Causes
- Open or shorted wiring to the line pressure solenoid
- Poor or corroded connector at solenoid or TCM/ECM
- Failed line pressure control solenoid (electrical or mechanically stuck)
- Faulty TCM/ECM or internal driver failure
- Low or contaminated transmission fluid causing solenoid sticking or incorrect pressure
- Damaged valve body or hydraulic blockage affecting solenoid response
Symptoms
- MIL/Check Engine light illuminated (transmission fault)
- Harsh, delayed or erratic shifting
- Transmission may go into limp/ failsafe mode with limited gears
- Loss of drive or slipping under load
- Unusual transmission noise or shuddering during shifts
What to check
- Read and record freeze frame and live data with a scan tool (monitor line pressure target vs actual, solenoid status, torque converter lockup, shift patterns)
- Retrieve all transmission-related codes and pending codes
- Visually inspect wiring harness and connectors for damage, corrosion, or pin push-out at solenoid and TCM/ECM
- Check and top up transmission fluid level and inspect condition (burnt smell, debris)
- Measure resistance of the line pressure solenoid at the connector with harness disconnected
- Backprobe solenoid connector and measure voltage/ground signal while commanding solenoid with scan tool
Signal parameters
- Static coil resistance (typical expected): roughly 6–25 Ω (varies by model) — compare to factory spec
- Operating voltage: 0 to battery voltage (0–12 V) when energized; many systems use PWM switching rather than steady DC
- PWM duty cycle or frequency: variable depending on commanded line pressure (scan tool should show duty % or commanded pressure)
- No-load open-circuit should show very high resistance/infinite; short to ground shows near 0 Ω
Diagnostic algorithm
- Connect a manufacturer-capable scan tool. Confirm P1737 and any related codes. Record live data for line pressure control and solenoid command.
- Visually inspect the solenoid connector and harness for corrosion, damage, or loose pins. Repair or reseat connectors as needed.
- With ignition off, disconnect the solenoid connector and measure coil resistance across the solenoid terminals. Compare to factory spec. Replace solenoid if out of range or open/shorted.
- With harness connected, backprobe the connector and measure voltage while commanding the solenoid ON/OFF from the scan tool. Verify proper switching (voltage or PWM) and good ground return.
- Check continuity between the solenoid connector and the TCM connector for opens or high resistance. Repair any wiring faults (splice, replace harness) as needed.
- If wiring and solenoid are good, check the TCM/ECM driver output. Swap with a known-good driver circuit only if service manual allows, or consult OEM diagnostics; replacement or reprogramming of TCM may be required.
- Inspect transmission fluid and valve body for contamination or debris; if fluid is severely degraded or valve body is suspected, consider fluid change, filter replacement, and valve body inspection/cleaning.
- After repairs, clear codes, perform relearn procedures if required, and road test. Monitor live data for proper line pressure control and absence of fault recurrence.
Likely causes
- Damaged/shorted harness or connector at the transmission
- Failed line pressure solenoid (electrical winding open or shorted)
- Corroded connector pins causing high resistance or intermittent contact
- Contaminated or degraded transmission fluid causing solenoid sticking
Fault status
Status
P1737 — Line Pressure Solenoid Circuit. Transmission control module detected an abnormal electrical condition in the line pressure solenoid circuit (open/short/intermittent or incorrect signal).
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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