Internal Fuel Injection Pump Controller Failure (Dodge)
What does P1688 mean?
The P1688 code means the vehicle's onboard diagnostic system has detected: Internal Fuel Injection Pump Controller Failure (Dodge). This is a critical severity code.
Common Symptoms
- Engine will not start
- Engine stalls and will not restart
- Check Engine Light on
- No fuel delivery to injectors
- White smoke from exhaust when cranking
Probable Causes (Ranked by Likelihood)
- Failed injection pump controller module Very High
- Corroded injection pump connector High
- Loss of power or ground to injection pump Moderate
- Internal injection pump mechanical failure Low
Step-by-Step Diagnostic Procedure
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Check for power and ground at the injection pump controller connector.
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Inspect the injection pump connector for corrosion, especially on vehicles exposed to road salt.
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Attempt to communicate with the injection pump controller using a scan tool.
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Verify the lift pump is providing adequate fuel supply pressure to the injection pump.
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If the controller has failed, the injection pump may need replacement or rebuilding.
Frequently Asked Questions
Is the injection pump controller the same as the VP44 pump?
The controller is the electronic brain of the VP44 injection pump. It is often the part that fails rather than the mechanical pump itself.
Can a lift pump failure cause P1688?
Yes. The VP44 pump requires consistent fuel supply pressure. A failing lift pump can starve the VP44, causing the controller to overheat and fail.
Should I add a lift pump if my truck does not have one?
Absolutely. Adding an aftermarket lift pump with a fuel pressure gauge is the best preventive measure against VP44 failure on Cummins diesel trucks.