U3785 Diagnostic Trouble Code

U3785 is a kind of OBD-II Diagnostic U-Network Diagnostic Trouble Code.

It is considered generic because it applies to all makes and models of vehicles, although specific repair steps may be different depending on your car model.

Symptoms

Symptoms of a U3785 diagnostic trouble code may include:

Hesitation upon acceleration
Excessive exhaust leak
Rich or lean exhaust
Lack of power

Possible Causes :

Faulty IMRC actuator relay (if equipped)
A large air leak at or near the number one oxygen sensor would also cause a lean mixture.
Some aftermarket accessories and performance modifications

Repair Processes :

Use the DVOM to test resistance and continuity on all system circuits if actuator and sensor resistance levels are in compliance with manufacturer's specifications. Look for missing ground strap or a rusty ground where the fuel tank is grounded to the frame. Check for damage to the wiring harness connector. Replace the oxygen sensor that is downstream from the catalytic converter on the side of the engine that does not contain cylinder #1. Also, if a oxygen sensor code stating "heater circuit malfunction" the sensor has most probably failed.

Process Tips

Diagnostic trouble code U3785 is not difficult to diagnose and repair. Thus, it always pays to have a qualified technician to look after your vehicle should this error code arise.

Diagnosing this code requires the engine to be in good running shape, without unmetered air entering the engine. If other codes that relates to misfiring condition, lean running or air entering the engine is present, then you must first fix those error codes before U3785.

Fortunately, U3785 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

U3785 Trouble Code For Specific Cars

U3785 Ginetta G4 Output Circuit Check Signal Low
U3785 Hyundai Matrix SCP (J1850) Invalid or Missing Data for Climate Control (HVAC)
U3785 Mercedes Gl Accelerometer Rear Circuit Failure
U3785 Hyundai Santamo SCP (J1850) Invalid or Missing Data for Displays
U3785 Chevrolet Deville Driver's / Passenger's Door Ajar Output Circuit Short to Battery
U3785 Opel Admiral Damper RF Circuit Open
U3785 Chevrolet Montana EGI Mini - MAF Failed Out Of Range