Spudd

Do i need new ecu

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Hi newby here.

Just purchased an 04 Lexus RX300.

The previous owner was going to scrap as he damaged some wiring fitting a set of air horns. The wiring has been repaired but the car refuses to start . My Delphi diagnostic showed me 10 fault codes ECU 10, P0102 Mass or volume air flow low A  Circuit low. P0112 intake air temp sens1 low,P0117 coolant temp sens 1 low,P0121 throttle pedal pos sens A circuit range, p0122 pedal pos sens A low, p0222 throttle pos sens / switch  B circuit low, p0560 system voltage, p0712 trans fluid temp sensor A circuit low, p2135 throttle pedal pos sensor /switch A/B voltage correlation , p2138 pos sensor D / E voltage correlation.

Any ideas or advice much appreciated.

Neil.

 

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Have you checked all fuses? Is the engine earthing strap fitted?

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2 hours ago, ColinBarber said:

Have you checked all fuses? Is the engine earthing strap fitted?

Checked under bonnet fuses passenger side. will search for other fuses and check earth strap. I had noticed there is a humming/whirring behind dash drivers side when key turned on.

Thank you for your input.

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Check the Battery is fully charged. Like other learned members have already pointed out, make sure the body, the engine, the gearbox and the ECU have a good ground. Remove the ground cables and clean the common contact areas so  the contact resistance is zero especially on the ECU.

Check that all connectors and connections to the various sensors have clean and corrosion free contacts.

Chris.

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2 hours ago, Mihanicos said:

Check the battery is fully charged. Like other learned members have already pointed out, make sure the body, the engine, the gearbox and the ECU have a good ground. Remove the ground cables and clean the common contact areas so  the contact resistance is zero especially on the ECU.

Check that all connectors and connections to the various sensors have clean and corrosion free contacts.

Chris.

Just spent the afternoon doing all that fitted a brand new Battery today. Other thing i noticed is doors unlock with remote but wont lock with fob just get an high pitched beep. also no sign of an immobilizer light when car is locked. engine turns over and just when you think its going to start ie nano second fire it carries on spinning.

Neil.

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Just had one of these but I will suggest it again.....insert key into ignition, turn to ignition and leave for 8 minutes, remove key, reinsert key then see if engine now starts. This process resets the immobiliser on earlier cars so it may work on yours, there again the number of fault codes may mean it doesn’t.

If it doesn’t I would have the ECU rig tested.

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Posted (edited)

Upon further consideration of the causes that you have the displayed codes, the ECU goes into limp mode when the range of the sensors is not within the parameters programmed to the ECU .

I would suggest before condemning the ECU, check that the voltage levels at the various sensors are available and the transmitted signals to the ECU are also available. P0102, 112,117 are caused due to being open or short circuited or due to the ECU malfunctioning.

Chris.

 

Edited by Mihanicos
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6 hours ago, Mihanicos said:

Upon further consideration of the causes that you have the displayed codes, the ECU goes into limp mode when the range of the sensors is not within the parameters programmed to the ECU .

I would suggest before condemning the ECU, check that the voltage levels at the various sensors are available and the transmitted signals to the ECU are also available. P0102, 112,117 are caused due to being open or short circuited or due to the ECU malfunctioning.

Chris.

Thank you will keep trying . tried the paper clip in obd port 4 and 13 as per made no difference have spark at plugs.

 

 

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Here below are Toyota/ Lexus OBD II pin assignments:

1 PS GND, Pin switched to ground

2 J1850+

5 GND  Ground

6 CAN +

7 K- line

9 PS GND, Pin switched to ground

12 PS 5, Pin switched to +5 v

14 CAN-

15 SCI

16 V Battery

Check that the respective data from each pin is available on the OBD II connector.

Chris.

 

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Have decided to bite the bullet and swap the ecu if that doesn't work then will cut my losses and dismantle.

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18 hours ago, Spudd said:

 

Scratch that I wont be beat.

Re ecu. if I get ecu,immobiliser, ignition barrel and key will I still need lexus to programme.

as below.

https://www.ebay.co.uk/itm/LEXUS-RX-IGNITION-KIT-89661-48530-275000-6432-89780-48010/163959928238?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

 

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