Internal failure of the fuel injection pump controller module; Faulty wiring or corroded connectors between the pump controller and the ECM; Poor ground connection for the fuel injection pump; Voltage supply issues to the pump controller, such as a blown fuse or relay; ECM software or internal fault misinterpreting the pump signal; Contaminated fuel or fuel system debris damaging the pump controller

DTC codes / Chrysler codes / P1688

P1688 · ChryslerInternal Fuel Injection Pump Controller Failure

Q: What does code P1688 mean?

Internal Fuel Injection Pump Controller Failure. P1688 on a Chrysler vehicle indicates that the internal controller inside the fuel injection pump has reported a failure to the engine control module (ECM). The ECM has detected that the pump's own control unit is no longer able to regulate fuel delivery correctly, which can affect engine performance and starting.

P1688 on a Chrysler vehicle indicates that the internal controller inside the fuel injection pump has reported a failure to the engine control module (ECM). The ECM has detected that the pump's own control unit is no longer able to regulate fuel delivery correctly, which can affect engine performance and starting.

SystemPowertrain

Code typeChrysler specific

SeverityHigh

Fix difficultyProfessional

AreaComputer and output circuits

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms
Engine may crank but fail to start, or start and then stall immediately
Rough running or misfiring under load
Reduced engine power or limp mode
Excessive fuel consumption or black smoke from the exhaust
Intermittent stalling while driving or at idle

Common causes, most likely first

Internal failure of the fuel injection pump controller module
Faulty wiring or corroded connectors between the pump controller and the ECM
Poor ground connection for the fuel injection pump
Voltage supply issues to the pump controller, such as a blown fuse or relay
ECM software or internal fault misinterpreting the pump signal
Contaminated fuel or fuel system debris damaging the pump controller

How to diagnose and fix it

Scan all modules for stored and pending codes to confirm P1688 is the primary fault
Inspect the fuel injection pump wiring harness and connectors for chafing, corrosion, or loose pins
Check the fuel pump fuse, relay, and ground connections for integrity and voltage drop
Perform a voltage and resistance test on the pump controller communication lines
Verify fuel pressure and volume to rule out mechanical pump issues
If electrical checks pass, replace the fuel injection pump controller or the entire pump assembly as required
Clear codes and perform a road test to confirm the repair

What P1688 really means for your Chrysler

This code often sets without any driveability complaint, so the first step is to check for related pending codes and freeze-frame data before condemning the pump.
A weak battery or poor charging system can cause the pump controller to log this fault, so always load-test the battery and check charging voltage first.
The pump controller is sensitive to heat and vibration; a failing controller may only act up when the engine is hot, so intermittent codes should be diagnosed with a hot engine.
Replacing the pump without checking the ground circuit at the pump mounting bolts is a common misdiagnosis, as a corroded ground can mimic a controller failure.
After replacement, some Chrysler models require a relearn procedure for the new pump controller, which a generic scan tool may not support.

Can I keep driving with P1688?

If the engine starts and runs normally, you can drive cautiously to a repair shop, but avoid heavy acceleration or long trips. If the engine stalls, runs rough, or enters limp mode, stop driving and have the vehicle towed to prevent damage to the pump or catalytic converter.

Tools that help

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Guidance is general and written for Chrysler vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.