My vehicle is simulating overheating. A check engine analysis reveals that it is a ECT sensor problem. Is this hard to change on a 2004 Chevy Express Van?

One possible reason for this could be a faulty engine coolant temperature (ECT) sensor. The ECT sensor tells the engine control module (ECM) the temperature of the engine coolant, which is used to adjust the air/fuel mixture for starting. If the ECT sensor is faulty, it may be sending incorrect temperature readings to the ECM, causing the engine to not start in cold weather.

Another possibility could be a weak fuel pump check valve. When the fuel pump check valve fails, it can cause the fuel pressure to drop when the engine is turned off, which can cause hard starting in cold weather .

It's also possible that the battery is weak and not providing enough power to start the engine in cold weather. Cold temperatures can reduce the battery's cranking power, which can make it difficult to start the engine.

I would recommend taking your vehicle to a certified mechanic to diagnose the issue.

P0118 - Engine Coolant Temperature (ECT) Circuit High Input Indicates the sensor signal is greater than Self-Test maximum. The ECT sensor maximum is 4.6 volts or -50°C (-46 °F). Note on some vehicles that are not equipped with an ECT sensor, CHT can be used and can set this DTC.

• Open circuit in harness
• Sensor signal short to power
• Damaged PCM
• Improper harness connection
• Damaged sensor

• Using signal simulation, disconnect sensor and simulate 1.0V on sensor signal circuit. Simulated 1.0V signal and scan PID voltage value should be similar. If voltage is similar check sensor, if voltage is not similar check related circuit and PCM

threw a po128 ??? Doesn't throw code's ,it stores code's . P0128 code does not tell you to replace the sensor either . With every code comes a diagnostic test procedure listed in a factory info. manual .
DTC P0128: Engine Coolant Temperature (ECT) Below Thermostat Regulating Temperature
The purpose of this diagnostic is to analyze the performance of the thermostat, by using the ECT sensor to determine if the engine coolant will increase at the correct rate, and also meet the calibrated target temperatures under various operating conditions. The ECM uses the start-up ECT and the start-up intake air temperature (IAT) to begin the diagnostic calculation. The air flow into the engine is accumulated, and vehicle speed, distance, and engine run time are also factored in to determine if the ECT does increase normally and reach the calibrated target temperatures.
Diagnostic Aids
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DTC P0128 occurring with insufficient vehicle interior heating is an indication of improper thermostat operation.

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Corrosion in the ECT sensor terminals or the ECT harness connector results in a greater voltage on the ECT sensor signal circuit, which is interpreted by the ECM as a colder ECT.

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A slight to moderate resistance in the ECT sensor signal circuit or low reference circuit will affect this diagnostic. This condition results in a greater voltage on the ECT sensor signal circuit, which is interpreted by the ECM as a colder ECT.

Circuit/System Verification

1. Ignition OFF, inspect the cooling system surge tank for the proper coolant level. Refer to Cooling System Leak Testing and Cooling System Draining and Filling .
2. Ignition OFF for 8 hours or greater.
3. Ignition ON, observe the scan tool ECT Sensor and IAT Sensor parameters. The ECT, IAT and ambient temperatures should be within 15?°C (27?°F) of each other.
Important: A critical analysis of the operation of the thermostat is necessary to properly diagnose this DTC.

4. Verify the proper heat range, and the operation of the thermostat. Refer to Thermostat Diagnosis .
5. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the ECT sensor.
2. Ignition OFF for 90 seconds, test for less than 5 ohms between the low reference circuit terminal B and ground.
?‡'
If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.

3. Ignition ON, verify the scan tool ECT Sensor parameter is colder than -39?°C (-38?°F).
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If warmer than the specified range, test the signal circuit terminal A for a short to ground. If the circuit tests normal, replace the ECM.

4. Install a 3A fused jumper wire between the signal circuit terminal A and the low reference circuit terminal B. Verify the scan tool ECT Sensor parameter is warmer than 149?°C (300?°F).
?‡'
If colder than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.

5. If the circuits test normal, test or replace the ECT sensor.

Forenza 2004
this is a Suzuki, id sell it, and is not even real Suzuki its a badged
product. actual. Daewoo Lacetti
Daewoo can't sell cars here so suzuki tries and fails... amazing car.

p0217 means overheated.
and when overheated power is lost. stop that or burn up the engine.
do the service on engine, 60,000 miles. steps.
and a new thermostat. i bet yours is 10 years old,,huh and END of life.
non last over that.
id sell it. when fixed, Suzuki's are no good.

FSM data.
Trouble Code Conditions:
Engine is running. Engine coolant temperature is higher than 50 Deg C (122 deg F). Intake Air Temperature (IAT) is higher than 35 deg C (95 deg F). Engine soak time is higher than 360 minutes, or start-up coolant temperature is less than 45 deg C (113 deg F). Engine Coolant Temperature (ECT) sensor reading is greater than 107 deg C (224.6 deg F).
Possible Causes:

• Sensor ECT
• Circuit
• ECM

the fsm skips bad thermostat. odd that... huh"?
and dead cooling fans.
and clogged radiator.
etc.
the first step is to see if it really is overheated, with a IR pyro gun.
if not, the ECT is bad
if is overheated, then fix that, as the ECT didnt lie.

simple , the sensor lied, (nah) or did overheat.

or air pockets at the ECT, low coolant actual.

P0117 - Engine Coolant Temperature (ECT) Circuit Low Input
The ECT (Engine coolant temperature) sensor is a thermistor located in the engine block or other coolant passage. It changes resistance with changes in temperature of the coolant that it's in contact with. It's usually a two wire sensor. One wire is a 5 volt reference from PCM (Powertrain Control Module) and the other is a ground supplied from PCM.

As the temperature of the coolant changes, the resistance of the sensor changes. When the engine is cold, the resistance is high. When the engine is warm, the resistance is low. If the PCM detects a signal voltage lower than the normal operating range of the sensor then P0117 code will set.


Potential symptoms include:
MIL (Malfunction Indicator Lamp) illumination
Poor fuel economy
Poor drivability
Engine may run rough or blow black smoke out the tailpipe
May not idle
May start and then die

Causes: Potential causes of the P0117 code include:
Bad ECT sensor
Short to ground on ECT signal circuit
Faulty or damaged connectors
Wiring harness damaged
Loose terminals at ECT or PCM
POSSIBLY an overheated engine
Bad PCM

Possible Solutions:
Since this code is for an abnormally low signal to the PCM from the ECT, the PCM saw a excessively "hot" condition in the engine coolant. This could be due to faulty ECT sensor or wiring, but it could, conceivably, be caused by an overheated engine.So if your engine was overheated diagnose that first. Having said that here are the possible solutions:

Using a scan tool, with KOEO (Key on engine off) check the ECT reading on the display. On a cold engine the ECT reading should match the IAT (Intake Air Temperature) sensor reading. If it doesn't, replace the ECT sensor.

1. If the ECT reading is showing an excessively hot reading, for example more than 260 deg. F, then unplug the ECT sensor. This should cause the ECT reading to drop to the extreme cold reading (around -30 deg.F or so). If it does, replace the sensor, because it's internally shorted. If it doesn't change the reading, the check for a short to ground on the signal circuit of the ECT wiring. It could be that the two ECT wires are shorted to each other. Look for any chafing or melted wiring. Repair as necessary.

a. If you can't find any wiring problems and the ECT reading doesn't drop to the extreme coldest when unplugged, then, check for voltage coming out of the PCM on the signal wire's pin at the PCM connector. If there isn't any voltage, or it is low, then the PCM may be bad. NOTE: On some models it is possible for the 5 Volt reference signal to be temperarily shorted. This can happen if an engine sensor internally shorts the 5 Volt reference. Since the 5 Volt reference is a "shared" circuit on many models, this will cause it to be abnormally low. Usually, though this will be accompanied by several other sensor codes. If you suspect that may be the case, unplug each sensor until the 5 Volt reference reappears. The last sensor unplugged is the offending sensor. Replace and recheck the signal wire from the PCM connector

2. If the scan tool ECT reading seems normal at this time then the problem may be intermittent. Use a "wiggle" test to manipulate the wiring harness and connectors while watching the ECT reading on the scan tool. Repair any wiring or connectors that are loose or corroded. You could check the Freeze frame data if your scan tool has that function. It will show the ECT reading when the failure occurred. If it shows the reading to be at the hottest extreme then replace the ECT sensor and see if the code reappears.

Hope this helps (remember to rate and comment this answer).

Would turn the key on no need to start it and unplug the ect engine coolant temp sensor. If fans come on then suspect a faulty etc which may not turn on the engine light. Which engine is in the vehicle so I can help locate the ect which is usually by the thermostat housing.

Your cooling fan relays are controlled by the Engine Control Module (ECM). What you are unplugging is probably the Engine Coolant Temperature Sensor (ECT). The ECM will default to "fans on" if it loses the circuit to the ECT. (It loses it when you unplug it) This is why the fans come on when you unplug the connector. The engine might be overheating because the ECT may be malfunctioning and "lying" to the computer about what the actual engine temperature is. If this is the case, the ECM is not turning the fans on because it doesn't "think" it is hot enough to need them. Then again, you could have a faulty temperature gauge that is making you think the engine is overheating when it is not. (If it is boiling over, then it is OBVIOUSLY overheating and you can just disregard that last statement.)
Anyway, the only way to properly diagnose the cooling system on your vehicle is to access the live engine data and look to see what temperature the ECM is seing while you take an actual reading with an infrared thermometer or a pyrometer and compare the two. Yhe thermometer or prometer reading should be within about 5 degrees of what the ECM "thinks" the temperature is. If there is a larger error than this then the coolant temp sensor should be replaced. If the reading is within this range and the temperatur gauge reads hot when it is not, then the gauge should be replaced.
Since the fans come on when you unplug the sensor, you know that all the fan circuits are working and the ECM is capable of controlling them, so it almost has to be a computer INPUT problem, not an OUTPUT problem.

P0117 - Engine Coolant Temperature (ECT) Circuit Low Input

The ECT (Engine coolant temperature) sensor is a thermistor located in the engine block or other coolant passage. It changes resistance with changes in temperature of the coolant that it's in contact with. It's usually a two wire sensor. One wire is a 5 volt reference from PCM (Powertrain Control Module) and the other is a ground supplied from PCM.

As the temperature of the coolant changes, the resistance of the sensor changes. When the engine is cold, the resistance is high. When the engine is warm, the resistance is low. If the PCM detects a signal voltage lower than the normal operating range of the sensor then P0117 code will set.

Potential symptoms include:
* MIL (Malfunction Indicator Lamp) illumination
* Poor fuel economy
* Poor drivability
* Engine may run rough or blow black smoke out the tailpipe
* May not idle
* May start and then die

Causes: Potential causes of the P0117 code include:
* Bad ECT sensor
* Short to ground on ECT signal circuit
* Faulty or damaged connectors
* Wiring harness damaged
* Loose terminals at ECT or PCM
* POSSIBLY an overheated engine
* Bad PCM

Possible Solutions: Since this code is for an abnormally low signal to the PCM from the ECT, the PCM saw a excessively "hot" condition in the engine coolant. This could be due to faulty ECT sensor or wiring, but it could, conceivably, be caused by an overheated engine.So if your engine was overheated diagnose that first. Having said that here are the possible solutions:

Using a scan tool, with KOEO (Key on engine off) check the ECT reading on the display. On a cold engine the ECT reading should match the IAT (Intake Air Temperature) sensor reading. If it doesn't, replace the ECT sensor.

1. If the ECT reading is showing an excessively hot reading, for example more than 260 deg. F, then unplug the ECT sensor. This should cause the ECT reading to drop to the extreme cold reading (around -30 deg.F or so). If it does, replace the sensor, because it's internally shorted. If it doesn't change the reading, the check for a short to ground on the signal circuit of the ECT wiring. It could be that the two ECT wires are shorted to each other. Look for any chafing or melted wiring. Repair as necessary.
a. If you can't find any wiring problems and the ECT reading doesn't drop to the extreme coldest when unplugged, then, check for voltage coming out of the PCM on the signal wire's pin at the PCM connector. If there isn't any voltage, or it is low, then the PCM may be bad. NOTE: On some models it is possible for the 5 Volt reference signal to be temperarily shorted. This can happen if an engine sensor internally shorts the 5 Volt reference. Since the 5 Volt reference is a "shared" circuit on many models, this will cause it to be abnormally low. Usually, though this will be accompanied by several other sensor codes. If you suspect that may be the case, unplug each sensor until the 5 Volt reference reappears. The last sensor unplugged is the offending sensor. Replace and recheck the signal wire from the PCM connector

2. If the scan tool ECT reading seems normal at this time then the problem may be intermittent. Use a "wiggle" test to manipulate the wiring harness and connectors while watching the ECT reading on the scan tool. Repair any wiring or connectors that are loose or corroded. You could check the Freeze frame data if your scan tool has that function. It will show the ECT reading when the failure occurred. If it shows the reading to be at the hottest extreme then replace the ECT sensor and see if the code reappears.

Other ECT sensor and circuit related DTCs: P0115, P0116, P0118, P0119, P0125, P0128

Hope this help to check and solve it.

This means that the engine's PCM detected that the engine has not reached the required temperature level within a specified amount of time after starting the engine. The intent of the P0128 code is to indicate a faulty thermostat. Similar codes: P0125

In determining the engine did not reach a "normal" temperature, it takes into account the length of time the vehicle has been running, the intake air temperature (IAT) sensor reading, the engine coolant temperature (ECT) sensor reading, and the speed of the vehicle.

A code P0128 may mean that one or more of the following has happened:

• Low engine coolant level
• Leaking or stuck open thermostat
• Faulty cooling fan (running too much)
• Faulty coolant temperature (ECT) sensor
• Faulty intake air temperature (IAT) sensor

Past experience indicates that the most likely solution is to replace the thermostat. However here are some suggestions on troubleshooting and repairing a P0128 OBD-II code:

• Verify coolant strength & level
• Verify proper cooling fan operation (check if it's running more than it should). Replace if necessary.
• Verify proper engine coolant temperature (ECT) sensor operation, replace if necessary.
• Verify proper intake air temperature (IAT) sensor operation, replace if necessary.
• If the above items check out good, replace the thermostat

REFERENCE: http://www.obd-codes.com/p0128

I hope this helps a bit!

Hi, could be the head gasket, have a compression test done to determine pressures etc, with the engine running see if you can smell exhaust fumes coming out of the radiator filler, good luck.