I have been working through the code on this ECM for a while. I plan to share information about this ECM here if there is interest. I have started with the analog bits that are written up here. I must thank a number of sources that have helped me find my way through the code. I will appreciate any assist that this list can give. As I get further along through the code, I will post here from time to time
I have just updated this post. More detail on unused A/Ds and an important correction re confusion about battery/ignition voltage. The multiplexers involved in all this analog switching are TI CD4051 or very similar. Manufacturer is TI for sure because of markings I recognize on the packaging. I believe the oxygen sensor interface makes use of another TI part LM9044. Can't be 100% on this, but the pinout and features match.
One last issue, I have a Motorola M68HC11 reference manual revision 3. There is an error in the chip pinout for the F1 variant: Pin 61 is incorrectly labeled as PE1/AN2 s/b PE1/AN1 later editions are corrected (time killer).
Thanks to members for help and corrections offered!
Cheers -Tom
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The 68HC11 has 8 channels of D/A on chip. The input port is designated "Port E". The eight inputs are designated PE0 through PE7. There are more than eight inputs to the 1997 Camaro ECM thus multiplexing is used on some inputs as below. Port G bits 0-2 select which of the inputs are connected to the A/D inputs PE5-PE7.
A/D PE0, NON-MUXED A/C pressure C4 Blue pin 12
I am not sure what is measured on with PE1, PE2, PE3 and PE4. In the 1997 Camaro with an M6, it would seem these are not used. There are a bunch of possibilities... I believe these inputs are not multiplexed.
A/D PE1, Default 0 Volt
A/D PE2, Default 0 Volt
A/D PE3, Default 0 Volt
A/D PE4, Default 0 Volt
The following inputs are measured through A/D inputs PE5 - PE7. They are multiplexed and reading is done once each eight calls of the routine. A CD4051 or similar is used to preform the multiplexing. A modulo eight counter is set up such that the analogs are updated on a round robin basis. The analogs are:
A/D PE5, MUX INPUT 0 Throttle position sensor C3 Clear pin 22 Mux1 pin 13
A/D PE5, MUX INPUT 1 Manifold absolute pressure C3 Clear pin 23 Mux1 pin 14
A/D PE5, MUX INPUT 2 Engine coolant temperature C3 Clear pin 25 Mux1 pin 15
A/D PE5, MUX INPUT 3 Intake air temperature C3 Clear pin 21 Mux1 pin 12
A/D PE5, MUX INPUT 4 Not used Default 0 Volt Mux1 pin 1
A/D PE5, MUX INPUT 5 Not used Default 0 Volt Mux1 pin 5
A/D PE5, MUX INPUT 6 Not used C3 Clear pin 27 Mux1 pin 2
A/D PE5, MUX INPUT 7 EVAP TEMPERATURE C4 Blue pin 24 Mux1 pin 4
A/D PE6, MUX INPUT 0 ALDL field service enable C4 Blue pin 20 Mux2 pin 13
A/D PE6, MUX INPUT 1 Not used Default 0 Volt Mux2 pin 14
A/D PE6, MUX INPUT 2 Knock sensor Knock filter pin 2 Mux2 pin 15
A/D PE6, MUX INPUT 3 O2 sensor From TI LM9044 chip Mux2 pin 12
A/D PE6, MUX INPUT 4 O2 sensor From TI LM9044 chip Mux2 pin 1
A/D PE6, MUX INPUT 5 Knock filter pin 1 Mux2 pin 5
A/D PE6, MUX INPUT 6 Not used Default 0 Volt Mux2 pin 2
A/D PE6, MUX INPUT 7 Not used Default 0 Volt Mux2 pin 4
A/D PE7, MUX INPUT 0 IGNITION VOLTAGE C4 Blue pin 3 Mux3 pin 13
A/D PE7, MUX INPUT 1 AUTO TRANS TEMP C4 Blue pin 28 Mux3 pin 14
A/D PE7, MUX INPUT 2 ENGINE OIL TEMP C4 Blue pin 26 Mux3 pin 15
A/D PE7, MUX INPUT 3 O2 sensor From TI LM9044 chip Mux2 pin 12
A/D PE7, MUX INPUT 4 O2 sensor From TI LM9044 chip Mux2 pin 1
A/D PE7, MUX INPUT 5 Not used Default 0 Volt Mux3 pin 5
A/D PE7, MUX INPUT 6 Not used Default 0 Volt Mux3 pin 2
A/D PE7, MUX INPUT 7 Not used Default 0 Volt Mux 3 pin 4
Oxygen sensors connect to the ECM with four wire pairs through the C3 (gray) connector pins:
3,4 Front left heated oxygen sensor (HO2S B1 S1)
7,8 Rear left heated oxygen sensor (HO2S B1 S2)
17,18 Front right heated oxygen sensor (HO2S B2 S1)
19,20 Rear right heated oxygen sensor (HO2S B2 S2)
These inputs connect to four TI lambda sensors. These interface chips have a number of features that both protect and provide default values int the event of faults. This tripped over this when trying to measure these inputs without ground referencing. The interface chips output a default voltage in this condition, which has no relation with the applied differential voltage (fault condition default). I can not be 100% certain of the chip number because only house numbers are marked. I believe them to be LM9904 Lambda Sensor Interface Amplifier.
A/D PE6, MUX INPUT 3 HO2S B1 S1
A/D PE6, MUX INPUT 4 HO2S B1 S2
A/D PE7, MUX INPUT 3 HO2S B2 S1
A/D PE7, MUX INPUT 4 HO2S B2 S2
A/C pressure sensor is referenced to the ECMs internal 5V reference and sensor ground. It is connected to the ECM through connector C4 (blue) pin 12. There is no multiplexer used on PE0.
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If you have any additions or corrections to this, or just want to comment Please PM me.
-Tom
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