Again With the Intermittent Issue. This Time Code 42
Thread Starter
|
Veteran
Joined: Aug 2013
Posts: 288
Likes: 1
Here's something to try.
Disconnect the negative battery cable.
Then, disconnect the ECU. Flush the contacts out with electrical contact cleaner.
Reconnect the ECU.
Then disconnect and flush again.
Reconnect.
Disconnect, put some "bulb grease" (dielectric grease) in the contact, and reconnect.
Reconnect the negative battery cable.
See how that does you.
Could be a bad contact; this cleans the contacts and packs the contacts with dielectric grease to slow down future corrosion and fretting.
(Also, remove/reinstall the ASD 2 or 3 times with the same cycle, to clean ITS contacts out.)
RwP
Disconnect the negative battery cable.
Then, disconnect the ECU. Flush the contacts out with electrical contact cleaner.
Reconnect the ECU.
Then disconnect and flush again.
Reconnect.
Disconnect, put some "bulb grease" (dielectric grease) in the contact, and reconnect.
Reconnect the negative battery cable.
See how that does you.
Could be a bad contact; this cleans the contacts and packs the contacts with dielectric grease to slow down future corrosion and fretting.
(Also, remove/reinstall the ASD 2 or 3 times with the same cycle, to clean ITS contacts out.)
RwP
That makes too much sense, thanks. i have used elec cleaner on the ecu connector one time but i did not do it twice, I'll do it twice this time and try the bulb grease.
Last edited by KevinSandidge; Feb 1, 2020 at 01:46 PM.
Thread Starter
|
Veteran
Joined: Aug 2013
Posts: 288
Likes: 1
Clear this up for me please: since i have no fuel pump relay, Would my ECU trigger a 42 asd code in response to a fuel issue? This one guy here is near convinced mine is a fuel related thing. And my fuel pump IS suspect. thanks
Last edited by KevinSandidge; Feb 1, 2020 at 01:47 PM.
Champion
Joined: Jan 2013
Posts: 4,737
Likes: 374
From: Northwest Louisiana
I'd suggest triple checking the wiring diagrams, but:
1) The ASD relay IS the fuel pump relay for a 1991.
2) Yes, it might; but. What code 42 is saying is that the expected voltage isn't getting into the ECU from the ASD.
3) The ones about the sending unit? They're not connected to the ECU on a 1991; and we don't have a BCM. So we can ignore those possible meanings.
4) IF the ASD was truly shorted, you'd also lose spark and fuel injection (since they're ALSO run off the ASD). I'd more guess that the ECU doesn't see the signal; that can be due to a corroded connection at one end or the other from the ASD to the ECU. So, let's clean up the contacts both ends before we start swapping parts. Contacts are the bane of any electronic circuit; they cause more intermittents and won't-fires than failed components historically.
Thankfully, for 1991, you CAN buy a fuel pump assembly; RockAuto lists several. I'd opt for the Denso or Bosch myself (I have not had good luck with Airtex or Carter in the past on my Malibu I used to own). Remember, cheap crap is cheap crap; buy good, but don't waste your money!
RwP
1) The ASD relay IS the fuel pump relay for a 1991.
2) Yes, it might; but. What code 42 is saying is that the expected voltage isn't getting into the ECU from the ASD.
3) The ones about the sending unit? They're not connected to the ECU on a 1991; and we don't have a BCM. So we can ignore those possible meanings.
4) IF the ASD was truly shorted, you'd also lose spark and fuel injection (since they're ALSO run off the ASD). I'd more guess that the ECU doesn't see the signal; that can be due to a corroded connection at one end or the other from the ASD to the ECU. So, let's clean up the contacts both ends before we start swapping parts. Contacts are the bane of any electronic circuit; they cause more intermittents and won't-fires than failed components historically.
Thankfully, for 1991, you CAN buy a fuel pump assembly; RockAuto lists several. I'd opt for the Denso or Bosch myself (I have not had good luck with Airtex or Carter in the past on my Malibu I used to own). Remember, cheap crap is cheap crap; buy good, but don't waste your money!
RwP
Thread Starter
|
Veteran
Joined: Aug 2013
Posts: 288
Likes: 1
You are the man; that explains a lot. thanks.
Now i remember putting in an Ebay pump, poor decision that. In fact, my buddy had to modify or do something to the pumps wiring, not sending unit wire but some other wires. does knowing that give you another thought maybe?
Look what i just read, do you concur
"Failure of the automatic shutdown relay is often shown as inexplicable stalling or refusal to start.Bohdan Bodnar noted, “The ASD can be triggered by a broken wire or short in another place, e.g. the fuel pump.” hmmm
Now i remember putting in an Ebay pump, poor decision that. In fact, my buddy had to modify or do something to the pumps wiring, not sending unit wire but some other wires. does knowing that give you another thought maybe?
Look what i just read, do you concur
"Failure of the automatic shutdown relay is often shown as inexplicable stalling or refusal to start.Bohdan Bodnar noted, “The ASD can be triggered by a broken wire or short in another place, e.g. the fuel pump.” hmmm
Last edited by KevinSandidge; Feb 2, 2020 at 10:43 AM. Reason: added new info
Thread Starter
|
Veteran
Joined: Aug 2013
Posts: 288
Likes: 1
Hey guys. I inspected my asd relay and the four prongs all were just a tad loose. I had to pay almost 30 bucks at orilys for a new one....the prongs on it were tight...I installed the new relay and ran the truck a short distance and now i am no longer getting the code 42. Maybe i caught a break!?!
Last edited by KevinSandidge; Feb 3, 2020 at 05:44 PM. Reason: correct grammer
Drive it for a while, and see what happens. 
Champion
Joined: Jan 2013
Posts: 4,737
Likes: 374
From: Northwest Louisiana
That would do it.
$30 at O'Reilly's? Ouch.
You may want to pick up a few generic SPDT relays from Amazon; I've used these https://smile.amazon.com/gp/product/B0748F1JK4/ and they'll plug right into the PDC if you don't install the tabs.
That set also has the sockets; that way you can go around wiring in relays to places (such as to improve the voltage to the headlights for better lighting) as you go on.
RwP
$30 at O'Reilly's? Ouch.
You may want to pick up a few generic SPDT relays from Amazon; I've used these https://smile.amazon.com/gp/product/B0748F1JK4/ and they'll plug right into the PDC if you don't install the tabs.
That set also has the sockets; that way you can go around wiring in relays to places (such as to improve the voltage to the headlights for better lighting) as you go on.
RwP
Champion
Joined: Jan 2013
Posts: 4,737
Likes: 374
From: Northwest Louisiana
I keep relays like that in stock; never know when I might want to have a switched 12V lead that's not fed through the ignition switch overloading it, for instance. 
I'm about to add one to the run I've added to the extra USB ports I've put in the passenger dash panel, so I can take any load from those off that poor 20A fuse that they're on now.
RwP
I'm about to add one to the run I've added to the extra USB ports I've put in the passenger dash panel, so I can take any load from those off that poor 20A fuse that they're on now.
RwP