What Does P1236 Mean?
DTC P1236 indicates the fuel pump secondary circuit is reading low voltage. The PCM or fuel pump driver module has detected that voltage on the secondary fuel pump circuit is below the expected threshold during operation. This can result in insufficient fuel delivery, particularly under load or at higher RPM where fuel demand increases.
Common Causes
30%
Corroded or high-resistance fuel pump connector at the tank
25%
Degraded fuel pump ground connection
20%
Fuel pump motor with worn brushes drawing excessive current
15%
Damaged wiring in the secondary fuel pump circuit
10%
Defective fuel pump driver module secondary output
Diagnostic Steps
1
Measure voltage at the fuel pump connector with the pump running under load — compare to specification and note any significant voltage drop from battery voltage.
2
Perform a voltage drop test on the fuel pump positive feed wire from the FPDM to the pump connector — more than 0.5V drop indicates high resistance.
3
Perform a voltage drop test on the fuel pump ground circuit — more than 0.3V indicates a poor ground.
4
Measure fuel pump current draw — compare to manufacturer specification. Excessive current draw indicates a failing pump motor.
5
Inspect the fuel pump connector and harness at the tank for corrosion, heat damage, or loose terminals. Clean or replace as needed.
Estimated Repair Cost
$100 - $650
Parts + labor, varies by vehicle and location
DTC P1236 indicates the fuel pump secondary circuit is reading low voltage. The PCM or fuel pump driver module has detected that voltage on the secondary fuel pump circuit is below the expected threshold during operation. This can result in insufficient fuel delivery, particularly under load or at h...
The most common cause of P1236 (Fuel Pump Secondary Circuit Low) is: Corroded or high-resistance fuel pump connector at the tank
Typical repair costs for P1236 range from $100 to $650, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Low voltage to the fuel pump reduces fuel pressure and volume, which may cause lean misfires and engine hesitation under load. In severe cases, the engine may stall during high-demand driving conditions.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1236 to identify the root cause.
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Quick Info
Category
Powertrain
System
Fuel Delivery
Difficulty
Type
Manufacturer
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