Toggle Side Panel

Shopping Cart

No products in the basket.

Shopping Cart

No products in the basket.

Close search
Home / DTC / P1789 — Pressure Control Solenoid B Short Circuit

P1789 — Pressure Control Solenoid B Short Circuit

Detailed page for trouble code P1789.

34,405codes
59brands
11,914generic
22,491specific
All codes P-codes (Powertrain) B-codes (Body) C-codes (Chassis) U-codes (Network/User) Tesla Alerts
Reset
Code

P1789

LINCOLN P — Powertrain

Pressure Control Solenoid B Short Circuit

Brand: LINCOLN
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Short to ground in the solenoid B wiring harness
  • Short to battery/ignition voltage in the solenoid B circuit
  • Damaged/chafed wiring or pinched harness
  • Corroded or loose connector at the solenoid or transmission harness
  • Failed pressure control solenoid B (internal short)
  • Faulty TCM/PCM driver transistor or internal electronics

Symptoms

  • MIL (Check Engine/Transmission) lamp illuminated
  • Harsh, delayed, or missed shifts
  • Transmission may go into limp/reduced-gear mode
  • No upshifts or stuck in a single gear
  • Poor fuel economy or loss of driveability
  • Possible transmission slipping or unusual shift feel

What to check

  • Retrieve freeze frame and all stored transmission codes with a capable scan tool
  • Check for related powertrain/transmission codes before proceeding
  • Visually inspect transmission harness and connector for damage, corrosion, melted insulation, or rodent chew
  • Inspect and secure grounds and battery positive feed/fuses for transmission electronics
  • With ignition ON (engine off) monitor live data for Pressure Control Solenoid B commanded state and feedback if available
  • Use a DVOM to measure resistance of the solenoid with connector disconnected (compare to spec)

Signal parameters

  • Solenoid coil resistance (approx): typically low ohms — commonly in the range of ~5–40 Ω (model dependent). Compare to OEM spec.
  • Command signal: TCM typically uses a switched ground or PWM to vary pressure; commanded line may show battery voltage when off and pull-to-ground when commanded (0–12 V swings depending on driver type).
  • PWM frequency (approx): commonly tens to a few hundred Hz (30–200 Hz typical).
  • Current draw: should be within the solenoid specification; a shorted coil will show abnormally high current and/or near-zero resistance.

Diagnostic algorithm

  1. Read and record P1789 plus any other stored codes and freeze frame data. Clear codes and attempt to reproduce.
  2. Visually inspect the solenoid B connector and harness from the transmission to the controller for damage, corrosion, or pinched wiring. Repair any obvious faults.
  3. With the ignition OFF disconnect the solenoid connector and measure coil resistance across the solenoid terminals. Compare to OEM spec; very low resistance indicates internal short, open indicates broken coil.
  4. With the connector disconnected, check for short-to-ground and short-to-battery on each control wire using an ohmmeter/voltmeter (check continuity to chassis ground and to battery positive).
  5. Reconnect and backprobe the control wire. With a scan tool command the solenoid ON/OFF and observe voltage and/or PWM and current. Look for unexpected constant 0 V (short to ground) or constant battery voltage (short to 12V) or no switching.
  6. Perform wiggle/strain tests on harness/connectors while commanding the solenoid to reveal intermittent shorts. Also inspect routing near exhaust, suspension, or sharp edges.
  7. If wiring and connectors test good and the solenoid coil has correct resistance, suspect the TCM driver. Verify supply voltages, fuses, and grounds. If supply and grounds are good but driver output is shorted, follow OEM TCM testing procedures.
  8. Isolate the circuit: unplug the solenoid and clear codes. If P1789 does not return, the solenoid or harness is likely at fault. If the code returns with the solenoid unplugged, suspect TCM/PCM or shared circuit short.
  9. Repair or replace the faulty component (repair wiring, replace connector, replace solenoid, or replace TCM as directed by further testing). Rebuild harness sections if necessary and protect routing.
  10. After repairs, clear codes, perform functional test and a road test to confirm proper shift quality and that code does not return.

Likely causes

  • Wiring insulation rubbed through and contacting chassis ground
  • Connector corrosion allowing intermittent short/high resistance
  • Solenoid coil internal short or coil degradation
  • Wire collapsed against a 12V source (short-to-voltage) after previous repair or harness routing issue

Fault status

⚠️ Status
P1789 — Pressure Control Solenoid B Short Circuit. Electrical short or overcurrent detected on transmission pressure control solenoid B circuit; causes abnormal pressure/shift control and may trigger limp mode.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.5-3.0 hours

Similar codes

P0796 P0776 P0756 P0762 P0705
166

Browse 166 LINCOLN manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

LINCOLN

Your experience will help others
+100 karma for a short comment :)
Keep it short and practical. Up to 500 characters.
Send to email

Report

Harassment or bullying behavior
Contains mature or sensitive content
Contains misleading or false information
Contains abusive or derogatory content
Contains spam, fake content or potential malware

Block Member?

Please confirm you want to block this member.

You will no longer be able to:

  • See blocked member's posts
  • Mention this member in posts
  • Invite this member to groups
  • Message this member
  • Add this member as a connection

Please note: This action will also remove this member from your connections and send a report to the site admin. Please allow a few minutes for this process to complete.

Report

You have already reported this .