Shift Solenoid 'B' Control Circuit Low
The P0998 code indicates that the Powertrain Control Module (PCM) has detected a low voltage condition in the control circuit of the shift solenoid 'B'. This solenoid is responsible for directing transmission fluid to engage specific gears. A low voltage reading suggests a short to ground, open circuit, or faulty solenoid, which can lead to improper transmission operation, harsh shifting, or failure to shift.
1. Symptoms You Will Notice
- Check Engine Light illuminated
- Transmission stuck in a single gear (limp mode)
- Harsh or delayed shifts
- Poor fuel economy
- Transmission slipping
2. Most Common Causes
- Faulty shift solenoid 'B'
- Open or shorted wiring in the solenoid control circuit
- Corroded or damaged connector at the transmission
- Low transmission fluid level or dirty fluid
- Failed PCM (rare)
3. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data. Clear codes and test drive to see if P0998 returns.
Step 2: Inspect transmission fluid level and condition; top off or replace if necessary.
Step 3: Visually check wiring and connectors for damage, corrosion, or loose pins. Repair as needed.
Step 4: Using a multimeter, test the resistance of shift solenoid 'B' (typically 20-30 ohms). Replace if out of spec.
Step 5: Check for voltage at the solenoid connector with the key on; if no voltage, test PCM output and wiring continuity.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended. The transmission may enter limp mode, limiting speed and causing unsafe driving conditions. Continued driving can damage the transmission.
How much does it cost to fix?▼
Repair costs typically range from $150 to $400, including parts and labor. Solenoid replacement is often $100-$200, plus diagnostic fees.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.