What Does P1243 Mean?
DTC P1243 indicates a malfunction in the fuel pump secondary circuit, representing yet another failure mode or detection criteria within the fuel pump power delivery system. This code may indicate the circuit is experiencing high-resistance conditions, voltage fluctuations, or control signal errors that prevent the FPDM from properly managing fuel pump output.
Common Causes
30%
Degraded FPDM power output MOSFET or transistor
25%
High-resistance splice or junction in the secondary circuit wiring
20%
Fuel pump connector terminal with micro-arc erosion
15%
Fuel pump at end of life with inconsistent current draw patterns
10%
Voltage regulator issue causing inconsistent supply to FPDM
Diagnostic Steps
1
Perform a comprehensive voltage drop test on both the positive and ground sides of the entire fuel pump secondary circuit with the pump under load.
2
Monitor fuel pressure over an extended drive cycle using a fuel pressure gauge — look for intermittent pressure drops that correlate with drivability symptoms.
3
Measure fuel pump current draw at idle and under load — compare to manufacturer specifications for both minimum and maximum current.
4
Inspect all in-line connectors and splices in the fuel pump secondary circuit for heat discoloration, corrosion, or mechanical damage.
5
If the pump and wiring test within spec, substitute a known-good FPDM to verify the module is not the source of the malfunction.
Estimated Repair Cost
$150 - $700
Parts + labor, varies by vehicle and location
DTC P1243 indicates a malfunction in the fuel pump secondary circuit, representing yet another failure mode or detection criteria within the fuel pump power delivery system. This code may indicate the circuit is experiencing high-resistance conditions, voltage fluctuations, or control signal errors ...
The most common cause of P1243 (Fuel Pump Secondary Circuit Malfunction) is: Degraded FPDM power output MOSFET or transistor
Typical repair costs for P1243 range from $150 to $700, depending on the vehicle, location, and whether you do it yourself or go to a shop.
This fuel pump circuit malfunction can cause unpredictable fuel delivery, potentially leading to engine stumble, hesitation, or stalling during critical driving moments. Prompt diagnosis is recommended.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1243 to identify the root cause.
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Quick Info
Category
Powertrain
System
Fuel Delivery
Difficulty
Type
Manufacturer
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