P1940 Daihatsu Sirion Diagnostic Trouble Code

P1940 Daihatsu Sirion code definition:
P1940 is a kind of OBD-II Diagnostic P-Powertrain Diagnostic Trouble Code for Daihatsu Sirion.

P1940 Daihatsu Sirion is described as Intake Air Temperature (IAT) Circuit Malfunction. It's actually a general trouble code for a problem on IAT electrical circuit sensor, as it sends incorrect voltage input signals to the PCM. Other serious codes may cause this code to pop up, and they may come with dangerous drivability issues that may expose you to safety risks and cause damage to the engine in the long run.

Symptoms

Symptoms of a P1940 Daihatsu Sirion diagnostic trouble code may include:

Hesitation upon acceleration
Excessive exhaust leak
Rich or lean exhaust
Engine surge

Possible Causes :

Rarely - faulty Powertrain Control Module (PCM-programming required after replacement)
Rough running engine due to misfiring plugs. Many engines have misfire codes to indicate the cylinder effected, such as P0307 for number 7.
Some aftermarket accessories and performance modifications

Common Misdiagnoses

IC Circuit High Voltage Problem
Control Module Throttle Actuator Position Performance Problem
Air Conditioning (A/C) Clutch Feedback Circuit High Voltage Problem
Cruise Vehicle Speed/Set Speed Difference Too High Problem
PCM Stack Overrun Problem

Repair Processes :

With the valve disconnected, the red voltmeter lead should be attached to the IMRC valve power wire and the black voltmeter lead connected to ground. Check to make sure they are not burnt or corroded. If in doubt, get some Electrical Contact cleaner at any parts store if cleaning of the terminals is needed. Look at the plug wires to make sure they are not burnt or laying on the exhaust.

Process Tips

Diagnostic trouble code P1940 Daihatsu Sirion 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 P1940 Daihatsu Sirion.

Fortunately, P1940 Daihatsu Sirion is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.