DTC P008B00 – Low Pressure Fuel System Pressure Too High
DTC P008B00 – Low Fuel Pressure (Low Pressure Circuit Too High / Low Pressure Fuel System Pressure Too High).
🔧 DTC P008B00 – Low Pressure Fuel System Pressure Too High
🔍 What the Code Means
The ECM detects that the low-pressure fuel supply (from tank to high-pressure pump) is higher than the calibrated limit.
This usually indicates a restriction, stuck pressure regulator, sensor fault, or wiring issue.
📌 Common Symptoms
Hard starting
Rough idle
Fuel smell near engine or tank
Poor acceleration
High-pressure fuel pump (HPFP) noise
Reduced power mode (in some cars)
🛠️ Possible Causes
1. Low-pressure fuel pump issues
Pump delivering too much fuel pressure
Incorrect pump type fitted
Faulty internal regulator
2. Fuel pressure regulator fault
Regulator stuck closed → pressure rises
Regulator filter clogged
3. Fuel pressure sensor failure
Sensor giving incorrect high readings
Sensor wiring/connector damaged
4. Fuel return line blockage
Kinked, pinched, or clogged return line
Blocked fuel filter (return-style systems)
5. Fuel contamination
Diesel contamination in petrol engines or vice versa
Excess debris blocking return flow
6. ECU reading error (rare)
🔧 Step-by-Step Diagnostic Procedure (Workshop Guide)
1. Scan Tool Live Data
Check:
Low-pressure fuel pump (LPFP) actual pressure
LPFP desired pressure
High-pressure fuel pump inlet pressure.
👉 If actual pressure > desired pressure, continue diagnosis.
2. Check Low-Pressure Fuel Pump Operation
Measure pressure at the low-pressure fuel line (before HPFP)
Most petrol: 3–6 bar
Most diesel: 4–8 bar
If pressure is too high, the LPFP or regulator is faulty.
3. Inspect the Fuel Pressure Regulator
Located on pump module or fuel rail Check for:
Stuck regulator valve
Electrical control issues (for electronic regulators)
If stuck closed, pressure will rise → Replace regulator.
4. Check Fuel Pressure Sensor (Low Pressure)
Inspect:
Connector pins for corrosion
Wiring for short to power/ground
Compare sensor reading with mechanical gauge
If mechanical pressure is OK but scanner shows high → sensor faulty.
5. Inspect Fuel Return Line
Look for:
Blockage
Kinked line under vehicle
Debris in fuel tank return valve
A blocked return will cause high pressure.
6. Check Fuel Filter
If filter is clogged, pump overworks and pressure rises → Replace filter.
7. Check for Fuel Contamination
Drain a sample:
Look for metal particles (damaged pump)
Water/diesel/petrol mix
🔧 Most Common Fixes
✅ Replace faulty low-pressure fuel regulator
✅ Replace low-pressure fuel pump
✅ Replace or clean clogged fuel filter
✅ Repair wiring to fuel pressure sensor
✅ Replace faulty low-pressure fuel pressure sensor
✅ Clear kink/blockage in return line
✅ Clean tank and flush contaminated fuel.
Welcome To Madurai Car Service 💐🙏.
