P1781 DTC - 2004 Chevrolet Aveo

Which of these engines does the vehicle have ?
Engine Controls - 1.2L
Engine Controls - 1.4L DOHC
Engine Controls - 1.4L SOHC
Engine Controls - 1.5L
Engine Controls - 1.6L (L91)

Has to be - 1.6L

DTC P0128 Engine Coolant Temperature (ECT) Below Thermostat Regulating Temperature
Circuit Description
The engine control module (ECM) monitors the temperature of the engine coolant for engine control and as an enabling criteria for some diagnostics. The amount of air flow into an engine is proportional to the amount of heat an engine generates. The ECM monitors the amount of air flow into the engine to calculate engine coolant temperature (ECT). The ECM uses the calculated temperature to determine if the engine has warmed up to the thermostat regulating temperature. If the coolant temperature does not increase normally or does not reach regulating temperature of the thermostat, diagnostics that use the ECT as enabling criteria, may not run when expected. If the engine coolant temperature fails to reach the thermostat regulating temperature, before a predetermined amount of air flow enters the engine, this DTC sets.

DTC P0441 Evaporative Emissions (EVAP) System Continuous Purge Flow
System Description
This DTC tests for continuous intake manifold vacuum flow to the Evaporative Emission (EVAP) System. The control module seals the EVAP system by commanding the EVAP canister purge solenoid valve Closed and the EVAP canister vent solenoid valve Closed. The control module monitors the fuel tank pressure (FTP) sensor to determine if a vacuum is being drawn on the EVAP system. If vacuum in the EVAP system is more than a predetermined value within a predetermined time, this DTC sets.

DTC P0700 Transmission Control Module (TCM) Requested MIL Illumination
This diagnostic trouble code (DTC) indicates that an emission related transmission DTC set in the transmission control module (TCM). The engine control module (ECM) receives the TCM DTC information over the serial data circuit. The ECM turns ON the malfunction indicator lamp (MIL) when the TCM sends a message over the serial data circuit requesting MIL illumination. The ECM will also store the freeze frame/failure records data for a transmission DTC. The DTC information for the ECM will only display DTC P0700, but the freeze frame/failure records data will display the transmission DTC that set.
DTC P1781
Conditions for Setting the DTC
• Transmission control module (TCM) detects that malfunction of engine speed signal for 2 seconds
• No DTC U2105
• Engine Misfire Detected

Does the speedometer work ?

Chevrolet Aveo getting code P1781 and P0700 both are manufacture please refer to the above website. Looks like a valve problem.

Get's voltage signal from the PCM - engine computer ! PCM connector 175B pin # 32 ,pin # 31 is return signal to PCM . This voltage is probably 5volt reference voltage , not battery voltage !
P1781 - 4x4L Switch Out of Self-Test Range Description: The 4x4L switch is an on/off switch. If the powertrain control module (PCM) does not sense low voltage when the switch is on, the DTC sets. Possible Causes:

• 4x4L harness open or shorted
• Damaged electronic shift module

Diagnostic Aids: Verify the 4x4L switch cycles on/off. Application Key On Engine Off Key On Engine Running Continuous Memory All Refer to the Workshop Manual Section 308-07A, Four-Wheel Drive Systems.

there is no p1781 code for dodge, http://www.datsc.com/tabid/122/OBD-Error-Code/P1781/Diagnostics/Dodge/Default.aspx

TYPE: 1999 Jeep OBD P1781

DTC P0113 - Intake Air Temperature Sensor High Voltage
To diag this code you will need a volt/ohm meter. Need to check for 5 volt reference in to sensor from PCM, and ground side of sensor to PCM. Also, check carefully the wires at the sensor. The wires may be broken inside the insulation, right at the connector of the sensor. Pull on each wire slightly and see if it starts stretch. If it does, then the wire is broke inside the insulation, and will need to be repaired.


DTC P0700 - EATX ControllerIs
Is a generic transmission control code. This code lets you know that a specific failure code is stored in the TCM (Transmission Control Module) and needs to be retreived with a diagnostic scanner with TCM reading capabilities. It may or may not be related to the ROM failure in the ECM (Engine Control Module).


DTC P1781 - Engine Torque Signal Circuit
This code is set during engine start up when the ECM and TCM do not communicate properly during initial power up. It will only illuminate the service light if the condition occurs in 2 consecutive start cycles, but the DTC will be stored in the failure records after the first cycle.


Hope this helps.

The transmission control module (TCM) uses the controller area network (CAN) to signal the engine control module (ECM) that the TCM is requesting malfunction indicator lamp (MIL) illumination. This happens when the TCM has determined that a failure that affects emissions has occurred in the transmission control system. When the ECM receives the correct message from the TCM, DTC P0700 will set.
Circuit Description
The engine coolant temperature (ECT) sensor is a variable resistor, that measures the temperature of the engine coolant. The ECT sensor has a signal circuit and a low reference circuit. The engine control module (ECM) supplies 5 volts to the ECT signal circuit, and a ground for the ECT low reference circuit. When the ECT is cold, the sensor resistance is high. When the ECT increases, the sensor resistance decreases. With high sensor resistance, the ECM detects a high voltage on the ECT signal circuit. With lower sensor resistance, the ECM detects a lower voltage on the ECT signal circuit. If the ECM detects an excessively high ECT signal voltage, which is a low temperature indication, DTC P0118 sets.

Diagnostic Aids
• If a short to a separate 5-volt source occurs this DTC may set.
• Use the Temperature vs Resistance table to test the ECT sensor at various temperature levels to evaluate the possibility of a skewed sensor. A skewed sensor could result in poor driveability concerns

Sounds like you need a new coolant temp. sensor , but test it ! Videos on youtube showing how to do it .
Circuit Description
To improve shift feel, the transmission control module (TCM) may request that the engine control module (ECM) reduce engine torque during shift events. When such a request is received, the ECM responds by retarding the base ignition timing and notifying the TCM that the request has succeeded. If the ECM is unable to comply with the request, the ECM sends the TCM a message that the request has failed.
The torque reduction request is sent to the ECM through a communication network called the controller area network (CAN). Two circuits are used to communicate CAN data between the ECM and TCM. A fault in the CAN will not cause DTC P1781 to set by itself. If a CAN fault occurs, other DTCs will set before DTC P1781.
When the TCM receives a torque reduction failure message from the ECM, then DTC P1781 will set. DTC P1781 is a type A DTC.

P1781 4x4 Switch Out Of Range

Couple things to check, transfer case and front diff fluids, make sure no wires are bare or shorting together on either transfer case or front diff, just to eliminate the easy stuff first. I would also check the connectors at the ECM and TCM just to make sure they are secure and tight.

Hope helps.

P0411 is secondary air incorrect flow. THis can be corrected by replacing the air bypass valve, GM # 9192121.

P1890 is the throttle position sensor (input)

P1781 is the engine torque signal circuit.

While driving should be ok I certainly wouldn't embark on a long road trip.

The Transmission shop lacks the skills and tools need to do the job. It's best to call around for a shop that has a proper scanner to talk to the TCM computer. The real trouble codes are in there. The best place would be a shop that has a ASE mechanic on duty or the Dealership.

Here what the two codes means:

P0700 Transmission Control System Malfunction
It means you have a trans control problem in the trans computer.
You will need to get it on a trans capable scanner to see what the trans code or problem is.

the P1781 is set during engine start up when the ECM & TCM do not communicate properly during initial power up. It will only illuminate the service light if the condition occurs in 2 consecutive start cycles, but the DTC will be stored in the failure records after the first cycle.