P1291 - High Side #1 (Right) Short to Ground or B+
The P1291 code indicates a short circuit in the high side driver circuit for the right injector bank (cylinder #1 on some engines). This can be a short to ground or battery positive voltage (B+). The high side driver is a transistor inside the powertrain control module (PCM) that supplies power to the injector. A short can damage the PCM or cause injector malfunction, leading to misfires and poor engine performance.
1. Symptoms You Will Notice
- Check Engine Light illuminated
- Engine misfire or rough idle
- Reduced fuel economy
- Possible hard starting or no start
2. Most Common Causes
- Faulty fuel injector (right bank, cylinder #1)
- Short to ground or B+ in wiring harness between PCM and injector
- Corroded or damaged connector at injector or PCM
- Failed PCM (internal short in high side driver)
3. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Visually inspect wiring and connectors for damage, corrosion, or shorts.
Step 3: Measure resistance of injector #1 (right bank) - should be 11-18 ohms.
Step 4: Check for short to ground or B+ at injector connector with key on.
Step 5: If wiring and injector are good, test PCM output or replace PCM.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended. Driving with a short can damage the PCM and cause further engine issues. Have it diagnosed and repaired promptly.
How much does it cost to fix?▼
Costs range from $150 to $400 depending on the cause. Injector replacement is $100-$200, wiring repair $50-$150, PCM replacement $200-$400.
5. Commonly Affected Makes
This is a manufacturer-specific code. The exact manufacturer is not confirmed in our current database.