Check engine light.. help!!

[SHO SPD]

I have had this problem for about 1 year now, the check engine light comes on intermitently and I pull a engine coolant temp sensor out of range and its a key on and engine running code. I have changed all 3 coolant temp sensors. I wouldnt think its a wire because its not a memory code. Any ideas?

 

[Rockledge]

DTC 114 IAT Sensor Out of Range

DTC 114 indicates that the corresponding sensor is out of the Self-Test range. Correct range of measure is 0.3 to 3.7 volts. Possible causes:

-- Ambient temperature below 10*C (50*F)

-- Faulty harness connector.

-- Faulty sensor.

-- Faulty PCM

Since the possible causes of DTC 114 are few, the pinpoint tests aren’t that long or complicated. Essentially, you need to check:

1. VREF - This is done by measuring the voltage between the VREF circuit and SIG RTN circuit at the at the TPS harness connector. (See: http://fordfuelinjection.com/index.php?p=30). A good VREF means the voltage should be between 4.0 volts and 6.0 volts.

2. IAT Resistance - This is done by measuring the resistance between the IAT sensor signal circuit and SIG RTN circuit at the temperature sensor and making sure it is within specs at different temperatures (See: http://fordfuelinjection.com/index.php?p=29).

3. IAT Harness Connector - Use your DMM and check for shorts or opens between the IAT and the PCM.. You’ll have to look up the pinouts for your SHO’s PCM to determine which pin numbers are for the IAT signal and SIG RTN (maybe try looking them up here: http://shoforum.com/diagrams/diagrams.htm). Shake and twist the harness to see if it’s an intermittent thing.

My ‘94 Ford Manual says that, if the above checks out, then it’s the PCM .

 

[SHO SPD]

Cool thanks, I will check all those out.

 

[SHO SPD]

ok, Rob94 told me to pull codes under normal operating temps. did that came up with
632 (R) E4OD - Transmission Control Switch (TCS) should be cycled once between engine ID and Goose test

I think thats just because I didnt put the car in neutral when testing. So after resetting the comp. I still get a CE light. But thats the only code I get unless the engine is cold, then I get..
116 (O,R) Engine Coolant (ECT) sensor out of range

Whats the deal?

 

[Ishodu]

Is the plug fully seated and connections clean?

 

[Rockledge]

Code 116 - ECT

The 114 and 116 codes are the same thing in terms of the pinpoint tests that I posted above. For some reason I got hung up on the 114 (ACT/IAT) code in that post, but the same exact tests apply to the ECT and the 116 fault code. So, you need to test VRef (at the TPS), the resistance of the ECT sensor at varying temps, and the integrity of the harness connector and circuit.

See: http://fordfuelinjection.com/index.php?p=28

FWIW, a short in the ECT signal circuit will result in approx. 0 voltage signal, while corrosion etc. will add resistance to the circuit and result in a signal voltage value that is higher than expected (since that value is actually based on voltage drop at the sensor). In each case a 116 code (out of range) will be set.

 

[SHO SPD]

Plug is fully seated and extremely clean.

I will check the resistance in the ECT tomorrow when I go to work. I replaced the sensor 2 times because I just thought they gave me a faulty one. I doubt the sensor is bad. So is the PCM still a possible problem?

 

[SHO SPD]

ok, sensors seem to have proper resistances with varying temps. So with those testing ok, does that leave the PCM to be at fault?

 

[projectSHO89]

If the engine is cold, you will ALWAYS get a 116 code during KOER.

If ambient temp is below 50F, you will get a 114.

The 632 indicates the computer did not see the OD switch cycle during the goose test. Check your timing of the test execution.

Steve

 

[rlw001]

Where are the all 3 sensors and what does each do?

I just replaced the sensor near the T-stat.

My issue is that the my dash guage is erratic and displays high temps.

My rad fan runs only with the AC on.

 

[Rockledge]

The IAT sensor is in the air filter box (IAT and ACT are the same sensor);

The ECT (for engine management control and cooling fan operation) is the 2-wire sensor near the T-stat housing;

The Temperature Sending Unit (for the gauge) is the 1-wire sensor near the T-stat housing.

The sending unit and ECT look fairly similar, the number of wires is the best way to be sure which is which.

 

[SHO SPD]

There is also one more below and towards the passenger side of the master cyl. close to the fire wall.