Hydraulic Pressure Unit Cycling Period Too Short
The P0943 code indicates that the powertrain control module (PCM) has detected the hydraulic pressure unit (HPU) cycling on and off too rapidly. The HPU is responsible for generating hydraulic pressure for systems like the transmission or brake booster. Rapid cycling can lead to insufficient pressure buildup, causing performance issues. This is often due to low fluid level, a faulty HPU, or electrical problems.
01. Most Common Causes
- Low hydraulic fluid level
- Faulty hydraulic pressure unit (HPU)
- Clogged hydraulic fluid filter
- Electrical issue (wiring, connector, or PCM)
02. Symptoms You Will Notice
- Illuminated check engine light
- Hard shifting or transmission slipping
- Brake pedal feels hard or requires more effort
- Unusual noises from the HPU
03. Step-by-Step Diagnosis
Step 1: Check hydraulic fluid level and condition; top off or replace if necessary.
Step 2: Inspect wiring and connectors to the HPU for damage or corrosion.
Step 3: Use a scan tool to monitor HPU cycling frequency and compare to specs.
Step 4: Test HPU operation by commanding it on/off with a scan tool; replace if faulty.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive with this code as it can lead to loss of power assist for brakes or transmission, increasing the risk of an accident.
How much does it cost to fix?▼
The cost to fix P0943 ranges from $150 to $400, depending on the cause. A simple fluid top-off is cheap, but replacing the HPU can be more expensive.