Question about 2003 Saturn ION
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.
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.
• 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 .
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.
Posted on Jun 10, 2017
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Posted on Jan 02, 2017
You are not the only one. Ive met a good many of Saturn owners (most were 2001 L300 drivers) but they were plagued with the problem you have and practically identical codes. The following remedies have been known to work:
1. Replacement Battery Cable
2.Replacement ECU Wiring Harness
3. Replacement of ECU
Posted on Mar 31, 2009
if you have a sunroof, the sunroof drains are clogged. either way you may have a bad door switch. you will have to pull each one out and look for corrosion at the plug. the fronts are most common, they are on either side of the dashboard.
Posted on May 27, 2009
There are a couple of bulletins from GM on valves causing these codes. # 05-06-01-030D and #PIP3063C are the bulletin #'s you need to have them look at. They are related to the valves in the cylinder head causing your exact symptoms. You should contact another dealer or GM customer assistance with this info. Good Luck
Posted on Jun 03, 2009
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