4 wire MAF voltage questions

Post by **subzerocarfanatic** » 31 Oct 2019, 16:40

abscate wrote: 27 Oct 2019, 15:43 ME7 is the name of the ECU software

All of th MAF wires run to the ECU except the 12V supply which goes to a common Bus with the fuel injectors

So the injectors and the MAF green wire is shared, both parts have voltage loss, so does that green wire go back to the fuse box on the shock tower or the main fuse box, also should i be tracing the ones going to the ECU since all the wires except green go there. i just got my emanual, trying to figure it out, its software form and is VIDAS,not easy for me to use.

Post by **abscate** » 31 Oct 2019, 18:56

There is no indication of anything wrong with the ECU

The battery voltage should be the same on the supply wire to both injectors and MAF.

If it isn’t, you trace it back to find the voltage loss using the wiring diagram.

Post by **subzerocarfanatic** » 03 Nov 2019, 12:18

All injectors read 12.5 ohms and the wiring plug for each injector reads 88 Mv, as does the green/orange stripe wire going to MAF plug
So if 23/11 is shared power node where is it getting it's power from, can't tell from the diagram. I assume 8/6, 8/7, 8/8, 8/9, and 8/10 are supposed to be the injectors.Is the power coming from 9/32 if so what does 9/32 represent

Post by **jimmy57** » 03 Nov 2019, 20:25

12-18 ohms depending on temp, colder is lower ohms. The issue is the power supply to injectors should be battery voltage and the other side of injector is an open circuit unless the engine control module (ecm) is grounding it to make it open and spray fuel in sequence. two things come to mind: 1. the wires from Pos battery terminal at battery to the fuse/relay box in front of left strut housing are problematic and 2. the relay for fuel system components in that same fuse/relay box can fail. The relay legend is on the box top.should be a yellow relay with terminals labeled 30 and 87 being wider blades that the 85 and 86 terminals. If you fashion a jumper lead and insert where 30 and 87 would go then the injectors and power wire at MAF should have battery voltage. If they don't then the red wires from pos terminal to box input post is likely the culprit. Battery acid can do a number on those red wires. You don't mention slow cranking or other problems so I assume a good charged battery and battery voltage more than 12V.

Post by **RickHaleParker** » 04 Nov 2019, 01:46

subzerocarfanatic wrote: 03 Nov 2019, 12:18 So if 23/11 is shared power node where is it getting it's power from, can't tell from the diagram.

Post by **abscate** » 04 Nov 2019, 04:09

If wires cross but don’t have either a dark dot or a circled X, they don’t connect.

You should be making voltage measurements, with the VOM on DC 12V scale

Post by **subzerocarfanatic** » 05 Nov 2019, 07:30

RickHaleParker wrote: 04 Nov 2019, 01:46
subzerocarfanatic wrote: 03 Nov 2019, 12:18 So if 23/11 is shared power node where is it getting it's power from, can't tell from the diagram.
2019-10-27 (2).png

Thanks for the input, I have already replaced the B+ battery cable going to the main junction post in the relay box on strut tower, the 4 red wires, I removed them and installed a single 4 gauge wire, they were corroded very bad. The relay you speak of jumpering is it the main control relay? I am pretty sure red relay #103 is fine, i can hear my fuel pump on when key is on, it never had any problems starting.

Post by **subzerocarfanatic** » 11 Nov 2019, 11:18

jimmy57 wrote: 03 Nov 2019, 20:25 12-18 ohms depending on temp, colder is lower ohms. The issue is the power supply to injectors should be battery voltage and the other side of injector is an open circuit unless the engine control module (ecm) is grounding it to make it open and spray fuel in sequence. two things come to mind: 1. the wires from Pos battery terminal at battery to the fuse/relay box in front of left strut housing are problematic and 2. the relay for fuel system components in that same fuse/relay box can fail. The relay legend is on the box top.should be a yellow relay with terminals labeled 30 and 87 being wider blades that the 85 and 86 terminals. If you fashion a jumper lead and insert where 30 and 87 would go then the injectors and power wire at MAF should have battery voltage. If they don't then the red wires from pos terminal to box input post is likely the culprit. Battery acid can do a number on those red wires. You don't mention slow cranking or other problems so I assume a good charged battery and battery voltage more than 12V.

So i make a jumper from 30 to 87 then turn the key on and check for voltage on the green/orange wire correct? I tried this and soon as the jumper was connected (with key off) I heard a clicking sound from the ETM then an audible tone. Isn't there a way to check the relay with my voltOmeter to see if the relay is good?

Post by **jimmy57** » 11 Nov 2019, 15:16

Yes, once jumper is in place then check the voltage. The click and the tne would be normal as the ETM did a self test and then went to a fixed part open position for engine cranking. Some of those large fuses in that row are the supply to the relays. It would be a good idea to look at those, or better yet remove them and check with ohmmeter for near 0 ohms (your meter may not get lower .4 or .5 ohms if you tocuh the leads to each other so whatever touched lead vlue is is the good value for fuse checks).

Post by **subzerocarfanatic** » 11 Nov 2019, 15:33

Ok, so check all the larger fuses in the relay/fuse main box for ohms . I have #1- # 4 in the secondary fuse box that are not showing 12 volts when all others seem to be,any ideas! thanks