Author Topic: Guide to main Calibra sensors and related issues.  (Read 11852 times)

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Bovva

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Guide to main Calibra sensors and related issues.
« on: October 09, 2009, 13:41:38 PM »
Here is a brief guide to sensors that are common on calibras and symptoms of them failing. Symptoms are highlighted in red.


Coolant Temperature Sensor

The coolant temperature sensor (CTS) is commonly found on modern injection engines. It measures the coolant (water) temperature in the engine itself, it is not to be confused with the thermostat as found on car radiators. The Engine Control Unit (ECU) uses the CTS value to calculate the ignition timing and injector pulse duration.
When the engine is cold the resistance increases. As the engine warms up, so too does the coolant and the resistance of the CTS decreases. This in turn returns a variable voltage signal (analogue) to the ECU based upon the coolant temperature.

The coolant sensor is a pretty reliable sensor, but if it fails it can prevent the engine control system from going into closed loop. This will result in a rich fuel mixture, excessive fuel consumption and elevated carbon monoxide (CO) emissions - which may cause the vehicle to fail an emissions test.



Crank Position / Cam Angle Sensor

There are two basic types of crankshaft position sensors: magnetic and Hall effect. The magnetic type uses a magnet to sense notches in the crankshaft or harmonic balancer. As the notch passes underneath, it causes a change in the magnetic field that produces an alternating current signal.
The frequency of the signal gives the PCM the information it needs to control timing. The Hall effect type of crank sensor uses notches or shutter blades on the crank, cam gear or balancer to disrupt a magnetic field in the Hall effect sensor window. This causes the sensor to switch on and off, producing a digital signal that the PCM reads to determine crank position and speed.


If a crank position sensor fails, the engine may still crank but it will not start. Most problems can be traced to faults in the sensor wiring harness. A disruption of the sensor supply voltage (Hall effect types), ground or return circuits can cause a loss of the all-important timing signal. The failing of this sensor can be intermittent and fail over a short period of time.


Knock Sensor

The knock sensor detects engine vibrations that indicate detonation is occurring so the computer can momentarily retard timing. Some engines have two knock sensors.

A failure with the knock sensor can cause spark knock and engine damaging detonation because the PCM will not know to retard ignition timing if knock is occurring.


MAF (Mass Air Flow) Sensor

The MAF sensor monitors the volume of air entering the engine. The sensor uses either a hot wire or heated filament to measure both airflow and air density.

The sensing element in MAF sensors can be easily contaminated causing hard starting, rough idle, hesitation and stalling problems. Cleaning a dirty MAF sensor with electronics cleaner can often restore normal sensor operation and save the cost of having to replace the sensor.


Lambda / O2 Sensor

The O2 sensor generates a voltage signal that is proportional to the amount of unburned oxygen in the exhaust. When the fuel mixture is rich, most of the oxygen is consumed during combustion so there is little unburned oxygen in the exhaust. The difference in oxygen levels between the exhaust inside the manifold and the air outside creates an electrical potential across the sensors platinum and zirconium tip. This causes the sensor to generate a voltage signal. The sensor's output is high (up to 0.9v) when the fuel mixture is rich (low oxygen), and low (down to 0.1v) when the mixture is lean (high oxygen).
Sensor output is monitored by the computer and is used to rebalance the fuel mixture for lowest emissions. When the sensor reads "lean" the PCM increases the on-time of the injectors to make the fuel mixture go rich. Conversely, when the sensor reads "rich" the PCM shortens the on-time of the injectors to make the fuel mixture go lean. This causes a rapid back-and-forth switching from rich to lean and back again as the engine is running. These even waves result in an "average" mixture that is almost perfectly balanced for clean combustion.

The O2 sensor's responsiveness and voltage output can diminish with age and exposure to certain contaminants in the exhaust such as lead, sulfur, silicone (coolant leaks) and phosphorus (oil burning). If the sensor becomes contaminated, it may not respond very quickly to changes in the air/fuel mixture causing a lag in the PCMs ability to control the air/fuel mixture.


All information was taken from various sources but should give you a good enough picture of how these these sensors work and common symptoms if they go wrong.


Offline Phil.

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Re: Guide to main calibra sensors and related issues.
« Reply #1 on: October 09, 2009, 15:41:15 PM »
A nice guide Shifty :)
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Offline Trigger

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Re: Guide to main Calibra sensors and related issues.
« Reply #2 on: October 09, 2009, 15:44:49 PM »
Cool. Topic put into relevant section :)

vix

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Re: Guide to main Calibra sensors and related issues.
« Reply #3 on: October 09, 2009, 17:51:08 PM »
Helpful and useful guide.

Believe it or not alot of people never look at the CTS as a cause!

Bovva

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Re: Guide to main Calibra sensors and related issues.
« Reply #4 on: October 09, 2009, 18:36:24 PM »
So many people experience sensor related issues with their motors but a lack of understanding what each sensor does just see's them ruled out straight away when a mechanical problem arises. Hopefully this brief guide will be of help to someone in the future.

Thanks Trig, wasn't sure if I put it in the right place :)

jacko-se9

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Re: Guide to main Calibra sensors and related issues.
« Reply #5 on: October 09, 2009, 20:33:14 PM »
Great content found very usefull, cheers

Offline Bazv6er

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Re: Guide to main Calibra sensors and related issues.
« Reply #6 on: October 09, 2009, 20:34:46 PM »
very good mate
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Offline boffin486

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Re: Guide to main Calibra sensors and related issues.
« Reply #7 on: October 10, 2009, 12:43:03 PM »
Instantly grabbed, converted to a Word document & saved with all my other useful stuff!  ;D

Still got the 16V Ecotec as well........... AND a mint shell waiting for a V6....

Offline bonggo72

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Re: Guide to main Calibra sensors and related issues.
« Reply #8 on: April 06, 2011, 11:53:27 AM »
Hi Shifty. Nice info there. Ecotec 2.0 16v '96. I'm having a fault w/ cam timing sensor on paper clip test. My engine runs fine and can rev up to red line (6,000 rpm). Got an automatic trany and still shifts good on sports mode. I there something I should worry about?

Bovva

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Re: Guide to main Calibra sensors and related issues.
« Reply #9 on: April 06, 2011, 15:26:43 PM »
Hi Shifty. Nice info there. Ecotec 2.0 16v '96. I'm having a fault w/ cam timing sensor on paper clip test. My engine runs fine and can rev up to red line (6,000 rpm). Got an automatic trany and still shifts good on sports mode. I there something I should worry about?

Start a new subject about your problem in the "troubleshooting" section mate and we'll try and help you solve the problem :)

Offline sealeysonic

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Re: Guide to main Calibra sensors and related issues.
« Reply #10 on: April 06, 2011, 23:22:29 PM »
Great Guide there mate...very intresting....thanks