Aygo Ecu ground location ?

[Frankla]

Yeah my last post was June 10th, been on hols and weather has been naff, anyway 1st problem was immo that was fixed 2nd problem started back end of May when the car started and drove for half an hour when I tried to restart it to come home it took 3 attempts, the next day it started but would cut out after about 30 seconds then it wouldn't start at all tried the spare key and it started reved OK and ticked over for about 30 seconds then cut out and didn't restart so I decided to link pin 4 and 13 for 35 minutes relink the immo but after 5 minutes with the ignition on the engine warning light started flashing very fast along with the throttle body I'll upload videos, Battery voltage OK alternator OK live and earths to the ecu are ok when cranking checked crank sensor, cam sensor, vvt Solenoid, put new plugs in it has a spark I'm running out of idea's, going to take top of the dash and instrument cluster and check all the plugs and connectors. 

 

 

 

[flash22]

ABS codes 38 and 39 - left and right rear abs sensors - may be caused by lack of use

MMT

95 - P0703 This relates to the brake light switch make sure you have power in and out on the 2 circuits one is normally closed the other is normally open

102 - U0001 short or open in the can bus, No comm between the ECU and TCU (MMT ECU)

 

as I said in a previous post something was taking down the CAN BUS - the MMT ECU is located under the dash up high on the driver's side by the A-pillar - check the connectors and wiring for corrosion and/or damage (rodent or water)

[Frankla]

Thanks for getting back to me, so check the can- and can+ from MMT to ECU to make sure it isn't shorted or a break in the cable 

[flash22]

The can bus is a serial bus its a point to multi point connection with terminations at the ends start with the visual inspections, the fault may well be in the MMT ECU or just corrosion i will need to look at the diagrams to see where the can bus goes to/comes from

[Frankla]

2 minutes ago, flash22 said:

The can bus is a serial bus its a point to multi point connection with terminations at the ends start with the visual inspections, the fault may well be in the MMT ECU or just corrosion i will need to look at the diagrams to see where the can bus goes to/comes from

These can bus cables here from MMT to ECU white and back cables, if these are damaged or the MMT ECU is fault would this make the not start just crank over 

[Frankla]

Is this the break switch circled in red 

[flash22]

a short/open will take down the can bus network so no comms between the modules, the engine will turn over but the ECU will get very confused,

not sure if the brake light switch will cause a no comms issue, as the MMT ECU need to see both switches - unplug the brake light switch and try to start the car

 

edit. the brake light switch has 4 pins (2 circuits) the switch you circled is the park/neutral switch

[Frankla]

6 minutes ago, flash22 said:

a short/open will take down the can bus network so no comms between the modules, the engine will turn over but the ECU will get very confused,

not sure if the brake light switch will cause a no comms issue, as the MMT ECU need to see both switches - unplug the brake light switch and try to start the car

 

edit. the brake light switch has 4 pins (2 circuits) the switch you circled is the park/neutral switch

Just saw the break light switch, thanks bob I'll check tomorrow. 

[Frankla]

The MMT ecu and plugs are clean no sign of water damage, I've checked the white and black can wire for continuity from the MMT ECU to the Engine ECU (Battery disconnected) shall I check these wires with Battery connected and ig on under load with a test lamp

[Frankla]

Doe the can bus wires only connect to the MMT ECU and the Engine ECU 

[flash22]

no, it's on the bus, check the powers and grounds on the mmt ecu you can also check the stop switch at the MMT ECU plugs

kgb10 mmt ecu pinout.pdf

edit. follow the black and white can wires. what is that green tape doing

[Frankla]

Thanks for the diagram very useful, rain stopped play 😠 the green tape looks like it's just keeping the can wires together, to check for a short on these CAN wires do I need MMT ECU and engine ECU disconnected, Battery connected and Ignition on or off using a multimeter? It looks like the wires go from the MMT ECU though the bulk head along to the fuse box to plug BA3 then to ECU. Can wires circled in red at fuse box

[flash22]

disconnect the Battery - unplug BA3 and check the plug and socket, check the continuity and resistance of the wiring between the MMT and BA3

[Frankla]

25 minutes ago, flash22 said:

disconnect the battery - unplug BA3 and check the plug and socket, check the continuity and resistance of the wiring between the MMT and BA3

Both MMT ECU and engine ECU plugged in with Battery disconnected? 

[flash22]

Unplug the MMT ecu and unplug the BA3 plug and test the wiring

[Frankla]

Checked the bus wires yesterday, I'm getting continuity and the resistance was 0.3 ohms on both wires, would the bus wires go anywhere else such as ABS came across this yesterday while searching a can junction connector A38 also I reconnected the Battery and both ECU's plugged my obd2 scanner in and I had a error code U0100 so I deleted the code and scanned again but no error code. 

[flash22]

A38 is only with VSC - Unplug the MMT ecu and see if you can talk to the ECU with the scan tool

U0100 is no comm so the scan tool is not seeing the ECU - 

further thoughts, the ACC is still an issue and it is not able to pull enough current, a worn ignition switch may be a issue - push the key in and up as you try to start the car as you have the dash apart check the ACC relay (white wire is control side power) check the voltage when turning the key

[Frankla]

Yeah I realised that A38 was for VSC today, the Battery voltage at the ignition barrel 13.1v then 12.8v acc then 12.6/7v ignition and round about 12v when cranking ill double check that tomorrow as for the U0100 code I think I unplugged A28 on the MMT when the when the Battery was connected, plugged scan tool in today they was no codes found, I shall unplug the MMT tomorrow to see if it can talk to the ECU and check the ig relay, thanks for your advice. 

[Frankla]

Forgot to mention I checked the bus wires at plug BA3 when everything was connected and was getting 61ohms if i disconnect either MMT or ECU i get 121 ohms at the BA3 plug 

[Frankla]

Voltages at ignition barrel, permanent supply 12.77v,ACC 12.48v,IG 12.55v, cranking around 11v. Voltage at IG relay 12.64v, when break pedal pressed 12.50v, when cranking around 11v. I unplugged MMT and scanner wouldn't connect plugged the MMT back in apart from the A28 plug then plugged the scanner back in and came back with a list of fault codes. Reconnected A28 plug rescanned and got no fault codes, do you think it worth having a look inside the ECU to see if there is any sign of damage. I done another flash back test linking pin 4 and 13 and the gearbox warning light was constantly flashing indicating no fault unlike the the last time showing fault code 95 (P0703) and 102 (U0001) 

[flash22]

with A28 unplugged did you try to start the car?, unplugging the MMT ECU will clear its codes

[Frankla]

No I didn't, didn't know if it would do something to the gearbox 

[Frankla]

Car doesn't start with A28 unplugged doesn't even crank, plugged in scanner and got fault codes related to the gearbox as I would have expected so I cleared codes and done another scan with everything plugged in no error codes, out of curiosity I unplugged the immo and camshaft sensor scanned the car again and got no error codes I thought I would have at least seen an error code for the immo b2799 like I had a few months ago when I had an issue with fuse number 11 (15amp) which I sorted, does number pin 7 at the diagnostic plug read the error codes. 

[flash22]

scan tool can't speak to the ECU with the mmt ECU plugged in (I assume you have mmt ecu fully plugged back in) but the MMT ECU will talk to the engine ECU to some degree

so something is pulling the can bus down from what we know it is the MMT ECU causing the problem

what is the part number on the MMT ecu

 

is the brake switch working correctly? One side is normally open and the other is normally closed and changes with the pedal being pressed

[Frankla]

Yeah that's right seems scan tool can't communicate with ECU while the MMT is plugged in, I'll try unplugging MMT and IMMO tomorrow to see if it brings IMMO error up as well as the gearbox errors, brake pedal seems to be working fine tested it at the MMT from the MMT pinout diagram.