Error code 0042

[9!'clipseDOHC]

My check engine light has been on ever since the first time I started up my car after my turbo swap which was about 10 months ago (or less). I just installed ECMlink and when I looked at my DTC's it was showing:

- 0042 - Fuel pump circuit malfunction
- 0025 - Barometric pressure circuit malfunction

I cleared the codes and then checked again and the 0042 code popped right back up. Any ideas on what this could be? The car has been running great (pre-ecmlink, since the install i've just been working on figuring out 'link and adjusting my idle[THANKS GOFER!!!])

My fuel pump is a Walbro 255 lph pump which I installed back in 2005. The fuel pump was rewired at the same time as the turbo swap (early 2010). The car does lose all fuel pressure when I shut it off and I have to crank it for several seconds before it will start if it has sat for more then a few hours. Once it's running the fuel pump seems to be working fine.

That's all the info I've got for now. Thanks!

 

[steve]

Fault code 42 is thrown when the ECU turns on the output to activate the fuel pump and doesn't see 12v on ECU pin 13.

Could be due to several causes, the pump could be pulling the feed voltage low, the MPI relay could be malfunctioning, the wiring harness broken, or the ECU might be damaged.

 

[9!'clipseDOHC]

Fault code 42 is thrown when the ECU turns on the output to activate the fuel pump and doesn't see 12v on ECU pin 13.

Could be due to several causes, the pump could be pulling the feed voltage low, the MPI relay could be malfunctioning, the wiring harness broken, or the ECU might be damaged.

I just got the ECU back from ECMtuning yesterday. They said the ECU checked out fine so we should be able to scratch that off the list. It's rewired so low voltage shouldn't be the issue, its possible though. I'll check the volts while its running.

Any easy way to check the MPI relay? I have a few spares but I don't know if they are working or not.

**UPDATE

I just checked the fuel pump and with the car off, fuel pump on, I'm getting 12.2 volts to the pump. Also now, and this just started right now, when I turn the key "on" the fuel pump comes on. Even when I deselect the fuel pump test on v3 it's still on. Not sure why.

My car is going crazy since installing link. I'm pretty sure its operator error though.

 

[steve]

If it were my car I'd pull out the wiring diagram and start checking to see if the ECU was pulling pin 56 low all the time or just when the pump should be on.
That pin 7 on the MPI relay follows pin 56 on the ECU and that pin 2 on the MPI relay provides 12v when pin 7 is low and nothing when pin 7 is also 12v.
ECU pin 13 should follow what you see at MPI relay pin 2.

With the ECU disconnected does the fuel pump run with the key on? (shouldn't)
Still with the ECU disconnected, do you get 12v on pin 3 of the MPI relay, key on? (should) Key off? (shouldn't)
With the ECU disconnected, do you see 12v at pin 7 of the MPI relay, key on? (should)
With the ECU disconnected and the key on, grounding pin 7 should turn the fuel pump on. It should stop when you remove the ground.

MPI relay pin 9 is from the starter circuit and should have 0v when your not cranking the car and 12 when you are. MPI relay pin 6 should be grounded all the time.

The fuel pump side of a 1G MPI relay has two inputs (coils) that activate the contacts.

One coil is between pins 3 and 7 and the other between pins 9 and 6. The FSM doesn't say what the resistance of the coils are but I'd expect that the resistance between the two pins be somewhere 30 to 100 ohms. They shouldn't be open or shorted. Connecting 12v to pin 3 or 9 and grounding pin 7 or 6 should cause the relay to click and the contacts between 3 and 2 to close.

When powering the coil between 9 and 6 you can measure the resistance of the contacts between 3 and 2 and it should be 0 ohms with the power between 9 and 6 and open when the power is removed.

Pin 3 is connected to both the coil and contacts so when testing the coil between 3 and 7 your looking for voltage at pin 2 not resistance so you don't damage your meter. With power between pin 3 and 7 you should have 12v at pin 2 and 0v without.

 

[9!'clipseDOHC]

Thanks Steve, I'm going to start checking those pins and I'll get back to you.

Also the deal about the fuel pump turning on with the key "on", for some reason even when I deselected the test fuel pump button on link it was still selected. It's off now and that's no longer an issue.

 

[9!'clipseDOHC]

When the key is off pin 56 ECU and 7 MPI have 0. Key 'ON', both get 12.1v. Pin 2 on the MPI seems have 12v all the time, at least until the MPI clicks. I can't get my leads into the pins with the ECU and MPI bolted down so I'm grounding the cases with alligator clips but I'm not sure if this is enough. With it grounded like that I'm having trouble connecting to the ECU via Link. Any suggestions on how to keep it grounded while I test it? I was unable to read any volts on Pin 13 of the ECU.

With the ECU disconnected does the fuel pump run with the key on? (shouldn't) NO
Still with the ECU disconnected, do you get 12v on pin 3 of the MPI relay, key on? (should) Yes Key off? (shouldn't) No
With the ECU disconnected, do you see 12v at pin 7 of the MPI relay, key on? (should) Yes
With the ECU disconnected and the key on, grounding pin 7 should turn the fuel pump on. It should stop when you remove the ground. Yes

Just to verify, pin 3 is black with a white strip and pin 7 is white with a red stripe correct?

 

[steve]

When the key is off pin 56 ECU and 7 MPI have 0. Key 'ON', both get 12.1v.

Pin 2 on the MPI seems have 12v all the time, at least until the MPI clicks.

I can't get my leads into the pins with the ECU and MPI bolted down so I'm grounding the cases with alligator clips but I'm not sure if this is enough. With it grounded like that I'm having trouble connecting to the ECU via Link.

Any suggestions on how to keep it grounded while I test it?

I was unable to read any volts on Pin 13 of the ECU.

With the ECU disconnected does the fuel pump run with the key on? (shouldn't) NO

Still with the ECU disconnected, do you get 12v on pin 3 of the MPI relay, key on? (should) No Key off? (shouldn't) No

With the ECU disconnected, do you see 12v at pin 7 of the MPI relay, key on? (should) Yes

With the ECU disconnected and the key on, grounding pin 7 should turn the fuel pump on. It should stop when you remove the ground. Yes

So the only problem so far is no juice to pin 3 (black wire with a green stripe) with the key on.

black wire with a green stripe is pin 2 on the MPI relay.
black wire with a white stripe is pin 3 on the MPI relay.
white wire with a red stripe is pin 7 on the MPI relay.
black wire is pin 6 on the MPI relay.
black wire with a yellow stripe is pin 9 on the MPI relay.

Your ECU should work unbolted from the car. The ground is provided by pins 101 and 106. No alligator clips should be needed.

No voltage on ECU pin 13 when the pump is on would explain the fault code.

 

[9!'clipseDOHC]

black wire with a green stripe is pin 2 on the MPI relay.
black wire with a white stripe is pin 3 on the MPI relay.
white wire with a red stripe is pin 7 on the MPI relay.
black wire is pin 6 on the MPI relay.
black wire with a yellow stripe is pin 9 on the MPI relay.

Your ECU should work unbolted from the car. The ground is provided by pins 101 and 106. No alligator clips should be needed.

No voltage on ECU pin 13 when the pump is on would explain the fault code.

OK I figured the colors out, I had already edited my post. I was looking at the wrong connector in the FSM. My MPI seems to be working correctly. I'll check pin 13 on the ECU again right now. For some reason when my ECU is unbolted I have trouble connecting to the ECU via link. Not sure why. Thanks so much for the help, as you can see I'm no pro when it comes to electrical issues.

 

[9!'clipseDOHC]

11.7 volts to pin 13 when the fuel pump comes on. Zero when the key is "on". So that's working too.

There is something loose on the ECU harness. And when the ECU is in a certain position its not making a connection. Also I noticed that the ISC motor would come on when I moved the wires which would be pin 67 and 68. I just pushed those in and it seems to be working fine now.

 

[9!'clipseDOHC]

11.7 volts to pin 13 when the fuel pump comes on. Zero when the key is "on". So that's working too.

There is something loose on the ECU harness. And when the ECU is in a certain position its not making a connection. Also I noticed that the ISC motor would come on when I moved the wires which would be pin 67 and 68. I just pushed those in and it seems to be working fine now.

Just to clarify, I was talking about the ECMlink connecting to the ECU, that is working fine now. Still getting the 0042 error every time.

 

[steve]

Still getting the 0042 error every time.

So at this point either the connector is bad so that the signal isn't getting into the ECU or we're back to the ECU again.

 

[9!'clipseDOHC]

The connector at the pump or at the ECU?

Could the fuel pump rewire have any affect on this?

 

[steve]

Fault code 42 is thrown when the ECU turns on the output to activate the fuel pump and doesn't see 12v on ECU pin 13.

11.7 volts to pin 13 when the fuel pump comes on. Zero when the key is "on". So that's working too.

If your seeing 12v at ECU pin 13 when the pump is on but your still getting the fault code after clearing it, then the signal is either not getting into the ECU (bad connector) or there is damage to the ECU and it's not seeing the signal.

 

[gofer]

+1 to a bad connection at the harness (since ECMLink just had the ECU), its possible that when its getting plugged into the ECU its pushing back into the harness and not getting the ECU that 12v. I helped a friend troubleshoot a similar problem and we suspected the ECU, so he sent it into Dave. They did everything to ensure the ECU was in tiptop shape, and it checked good! We were left scratching are heads until we looked at the harness closer and realized that pin was pushing in...

 

[9!'clipseDOHC]

If your seeing 12v at ECU pin 13 when the pump is on but your still getting the fault code after clearing it, then the signal is either not getting into the ECU (bad connector) or there is damage to the ECU and it's not seeing the signal.

+1 to a bad connection at the harness (since ECMLink just had the ECU), its possible that when its getting plugged into the ECU its pushing back into the harness and not getting the ECU that 12v. I helped a friend troubleshoot a similar problem and we suspected the ECU, so he sent it into Dave. They did everything to ensure the ECU was in tiptop shape, and it checked good! We were left scratching are heads until we looked at the harness closer and realized that pin was pushing in...

Ok, I'll check that tomorrow. Got to work now. I'll also double check the voltage at pin 13 to be absolutly sure. When I checked it I had the key "on", the ECU conected to my laptop, I pressed the probe into the harness from the wire side, and clicked the fuel pump test box on ECMlink, that's when I got the 11.7 volts. Thanks again for all the help, both of you guys rock!

 

[gofer]

If the voltage is on the pin that doesn't mean the ECU is seeing it, thats why I think its the harness, the pin pushes back into the connector when it gets plugged in.

 

[9!'clipseDOHC]

Pin 56 (white with red) Key off - 0 volts, Key on - 12 volts, pump on - 0 volts.
Pin 13 (black with white) Key off - 0 volts, Key on - 0 volts, pump on - 11.7 volts.

After messing with the ECU and harness though, the car wouldn't start and I was getting the following DTC's:

0014 Throttle position circuit malfunction
0021 Engine coolant temperature circuit malfunction
0025 Barometric pressure circuit malfunction

I messed with the harness some more to make sure the connections were good and taped it up near the connectors so the wire wouldn't be able to move around. After that it took me a while to get it to start and it then it was running like crap. It was idle surging (which it doesn't do), going from closed loop to open loop, and showing a coolant temp of -74 degrees. I think I read something about the coolant temp showing negative temps on another thread, I'll have to look an see. Here's the log of it acting retarded:

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Also the only DTC now is the good old 0042 fuel pump circuit malfunction. It certainly seems like my wire harness is a mess but everything looks and feels fine. It doesn't appear loose and hacked, although it's sure acting like it is.

 

[gofer]

I wonder if you've got a shorted/partial short to the ECU's sensor ground. How do you have your WB o2 gauge wired into the ECU, what wires going to which pins?

Everything I see in that log is no question a blown sensor ground, maybe Steve can add something though.

Coolant Temps = -74*
TPS Voltage = 0v
Baro = 0.3 in/Hg
ISC Position = 0
Intake Temp = 63*
MAF = 76 Hz
front o2 = 0.2 to 0.8v​

 

[9!'clipseDOHC]

I wonder if you've got a shorted/partial short to the ECU's sensor ground. How do you have your WB o2 gauge wired into the ECU, what wires going to which pins?

WB isn't wired into the ECU at all yet. It gets power from the fuse box and is grounded to the chassis. That's it.

 

[gofer]

Thats good news then, some wire their WB gauge to the ECU's sensor ground and blow it. You're going to have to pull out a multimeter and start checking continuity across your harness, let me pull open a wiring diagram and get a good pin out for you quick.

I'm wondering if one of your ECU sensor ground wires is having connection issues rather than a blown ECU ground, there are two which are located at pin 17 and 24.

 

[9!'clipseDOHC]

I'll go check those now.

 

[gofer]

Alright, check continuity with a DMM between the following sensors and the ECU sensor ground.

1. TPS connector pin (4) GRN/BLK wire to ECU pin 17 & 24 GRN/BLK wires.
   
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2. MAF connector pin (4) GRN/BLK wire to ECU pin 17 & 24 GRN/BLK wires.
   Turbo -
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   N/T -
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3. ISC connector pin (3) GRN/BLK wire to ECU pin 17 & 24 GRN/BLK wires.
   
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4. CTS GRN/BLK wire to ECU pin 17 & 24 GRN/BLK wires.

 

[9!'clipseDOHC]

Pin #17:
1. Yes,
2. Pin 6, not 4
3. None.
4. Yes

Pin #24:
1. Yes
2. Pin 6, not 4.
3. None
4. Yes.

On the TPS diagram, thats like looking at the plug from the plug side, not the wire side. The turbo MAF diagram is opposite, looking at it from the wire side. I say this based on the location of the blank pins. On the ISC I checked all the pins and none had continuity. There is also NO green/black wire on the ISC plug.

 

[gofer]

I think my ISC checks were off, I'm looking through the wiring diagrams and trying to figure out what the Motor Position Sensor is... I thought it was the ISC since it was a (6) pin but I don't think thats right. It would make sense that is was the CAS, thats only (4) pin though...

Figured it out. The MPS was on the 1.8l N/T DSM's, I wonder why my ECU wiring diagram was showing it for the turbo platform. Damn.

 

[9!'clipseDOHC]

Well besides that everything else checks out for the sensor grounds then. I'm going to try to start it again.

Still not starting. Data log still shows -74 degrees for the coolant temp. Only DTC is 0042, fuel pump.