P0233
Fuel Pump Secondary Circuit High
Powertrain Fuel and Air Metering Fuel pump circuit 🟡 Moderate — Fix within a week
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What This Actually Means
In plain language — no jargon

The fuel pump's secondary circuit is detecting too much electrical current or voltage, similar to a water pump working too hard against a closed valve. This usually means a wiring short, relay problem, or fuel pump drawing excessive current.

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Symptoms You May Notice
3 known symptoms for this code
Check Engine Light illuminated
Engine cranks but won't start or stalls while driving
Fuel pump runs continuously or makes abnormal noise
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Embedded Systems Insight
What the ECU/ECM is actually computing

The ECM monitors the fuel pump circuit's voltage and current draw through the fuel pump relay. When voltage stays abnormally high or current exceeds safe operating limits, the fault is triggered. The ECU expects the circuit to draw current only during cranking and running, with voltage dropping appropriately across the relay.

Voltage & Parameter Thresholds

Parameter Normal Range Fault Condition
Fuel pump circuit current 0-15 amps during operation Above 15 amps or sustained high draw
Fuel pump relay voltage drop 0.5-1.5 volts across relay Below 0.5V or above 1.5V
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Diagnostic & DIY Fix Guide
Check these in order — from cheapest to most complex
1
Battery terminals and fuel pump ground wire
Clean corroded battery terminals and inspect the fuel pump's ground wire for loose or corroded connections.
2
Fuel pump relay
Locate and swap the fuel pump relay with an identical relay from another circuit to test if the fault moves.
3
Fuel pump wiring harness
Inspect the fuel pump power and ground wires for cuts, abrasion, or pinching that could cause a short to ground.