P189B

Code

Generic P — Powertrain

Shift Solenoid 'B' Control Circuit Range/Performance

Brand: Generic

Type: P — Powertrain

Views: UK: 18 EN: 22 RU: 29

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Open or short in solenoid 'B' wiring (power or ground)
Poor connector connection or corrosion at solenoid or TCM connector
Faulty shift solenoid 'B' (coil electrical failure or internal mechanical sticking)
Low, dirty, or incorrect transmission fluid affecting hydraulic response
Damaged valve body or internal hydraulic passages linked to solenoid 'B'
Faulty TCM/PCM driver output or internal electronics

MIL/Check Engine lamp illuminated
Harsh, delayed, or missed shifts involving gears controlled by solenoid B
Transmission stuck in limp/safe mode or limited gear range
Unusual transmission noises or slipping under load
Stored P189B and possibly other transmission-related codes
Intermittent transmission performance that may change with temperature or vibration

Read and record all stored/transient DTCs and freeze-frame data with a scan tool
Inspect transmission fluid level and condition (color, odor, contamination)
Visually inspect wiring harness and connectors for damage, corrosion, or loose pins at solenoid and TCM
Backprobe solenoid 'B' connector while operating to verify command voltage/pulse and ground
Measure solenoid coil resistance with ohmmeter and compare to manufacturer spec
Wiggle test harness while monitoring live data to look for intermittent faults

Drive type: usually PWM (pulse-width modulated) from TCM; not a steady DC for most modern systems
Typical command voltage range: 0–12 V (depending on vehicle/driver design)
Common PWM frequency range: roughly 20–250 Hz (varies by manufacturer)
Expected coil resistance: commonly in the tens of ohms (often 5–50 Ω); check specific vehicle spec
When commanded ON the voltage will show pulsed/high duty; when OFF it will be low or grounded

Use a scan tool to confirm P189B is current or historic; record freeze-frame and related transmission codes.
Check transmission fluid level/condition and correct if low or severely contaminated; do not ignore signs of contamination.
Perform a visual inspection of solenoid B connector, wiring and TCM connector for corrosion, bent pins, or heat damage.
With ignition OFF disconnect solenoid B connector. Measure coil resistance between the two solenoid pins; compare to spec. Replace solenoid if out of range.
With key ON (engine off) backprobe the connector and command the solenoid using a scan tool while monitoring voltage/ground to verify the TCM is commanding and the circuit completes.
Check continuity from solenoid connector to TCM pin and for shorts to battery voltage or ground. Repair any open/short, terminal damage or corrosion.
If wiring and solenoid test good but the circuit is still out of range, use an oscilloscope on the TCM output to verify PWM waveform and driver behavior under load.
If waveform is absent or shows abnormal driver behavior, suspect TCM driver fault—confirm by swapping with identical solenoid circuit (if available) or consult manufacturer guidance before replacing TCM.
If solenoid electricals are good but shift performance still poor, inspect valve body and hydraulic passages for contamination or mechanical sticking; replace/clean as required.
After repairs clear codes and road test under varied conditions; re-scan to ensure fault does not return.