I'm having trouble with my 87 firebird 2.8 MFI. I have a code 54 the check engine light stays on even when I check the codes it just gets brighter when displaying the codes. Anyway I know the code is low voltage to the fuel pump but what causes it and is it also the reason i'm only getting about 10-12 mpg.
Any help would be appreciated.

 

(sigh) Well, here's the code 54 chart. Do me a favor and go through it, alright? Nobody's bothered with it yet. I'm not sure why I typed it up from my GM book. It only seems complicated, just print it out and bring it outside. I even made it easier when I typed it by describing where every wire is! You don't get -that- from the GM service manual. Oh and welcome to the board!! Anyway, here's the chart:

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DIAGNOSTIC CHART FOR CODE 54 (2.8L MPFI ENGINE)
---------------------------typed by Tom P------

Preliminary stuff:

Ignition off for ten seconds.
Ignition ON, listen for in-tank fuel pump
Fuel pump should run for 2 seconds after ignition on

Not ok? See "1"
Okay? See "6"

1. Ignition off. Remove the fuel pump relay, but keep the harness connected. This is
____located on the top of firewall, driver's side, on a relay bracket. It's the leftmost
____relay, with a connector that has these wires: Tan/white, black/white, green/white,
____orange, orange.

____Backprobe terminal "A" (that's tan/white, circuit #120) with a test light to ground,
____make sure you can see the test light from the driver's seat. Turn the Ignition to
____on (don't crank the engine/start the car). The light should turn on within 2 seconds.

____Light on? See "1A".
____Light off? See "2".

___1A: Repeat the test on CKT 120 (tan/white) at the rear body connector. You saw this
________connector when you replaced the fuel pump, it's in front of the tank, against the
________top of the underside of the car.

________Light on? Faulty pump ground or pump (ouch!)
________Light off? Fix the open (break) in circuit 120.

2. Disconnect the pump relay. Put the ignition on, engine stopped. Probe the fuel pump
____harness connector, terminal "E" (orange on the edge of the connector, Circuit 340)
____with a test light to ground.

____Light off? See "2A"
____Light on? See "3".

___2A: Repair open in CKT 340, this comes off of both your "computer-and-oil-pressure-
________safety-switch" setup and your "fuel-pump-and-computer-fuse".

________Your fuel pump/ECM fuse is under your hood, screwed down to the upper-frame-rail
________on the passenger side of the car, close to the air cleaner & black fuel-vapor-can.
________You'll see two little black boxes, each with two wires coming out of them, screwed
________down to the upper frame rail by one screw each. One of them has a red wire and an
________ORANGE wire coming out of it- that's your pump/ECM fuse holder. Pop the top off
________to see the fuse. (The holder with red & brown wires is for your MAF sensor.

________Now, two things could happen here. You could have a bad fuel pump fuse- check the
________fuse. If it looks okay, replace it anyway... sometimes a fuse can look good, but
________really be blown. The second possibility- I want you to probe the red wire on the
________fuse holder with a test light to ground. The red wire goes to the positive-
________junction-block on the radiator support- your pump/ECM fuse might not be getting
________any power! If the light doesn't light, check the red wire hookup. However, with
________either case your computer would be acting up, too, and I don't think you could get
________the car to start at all.

3. Connect a test light beteween pump connector pin "B" (black/white wire, CKT450) and
____pin "E" (orange wire from step 2, CKT340).

____Light off? See "3A"
____Light on? See "4"

___3A: Repair open CKT 340. The black/white wire isn't making a good ground. Sorry, I
________don't know where this grounds out to. I'd imagine it goes to a screw on the car.

4. Connect test light between pump connector terminal "C" (dk green/white wire, CKT 465)
____and ground. Ignition to "off" for 10 seconds. Note test light within 2 seconds after
____ignition "on".

____Light on? See "4A"
____Light off? See "5"

___4A: Faulty Relay! Hey that's cool, a $10-$15 part from the dealer...
________The manual continues to test the "oil pressure safety switch", I'll put
________that test at the end of this message.

5. Ignition "off". Disconnect ECM A-B connector and check for an open, or a short to
____ground, in circuit 465- that's the dark green/white wire from the relay. It's on
____terminal "A1" of the ECM A-B connector.

____CKT 465 okay? See "5A"
____CKT 465 Bad? See "5B"

___5A: Check resistance across pump relay pins "opposite harness connector terminals B
________and C". Should measure 20 ohms or more to be good.
___________Resistance good? Faulty ECM A-1 connector, or bad ECM
___________Resistance bad? Replace Relay AND ECM.


___5B: Fix CKT 465. If CKT 465 was shorted to ground, re-check for a light "on"
________between harness connector terminal "C" and ground within 2 seconds after ignition
________"on".
___________Get a light? Cool, reconnect your relay
___________No light? Faulty ECM terminal "A1", or bad ECM.

6. Clear codes. Start engine and note service engine soon light. If the light comes
____on, check the code, if it's not 54 or you don't get a light, it's something else
____wrong, or an "intermittant" problem. But you get the code, so I shouldn't have
____even bothered typing this.

7. Backprobe ECM terminal "B2" (that's tan/white, CKT 120) with a test light to ground.
____Ignition off for 10 seconds. Note light within 2 seconds after ignition on.

____Light on? See 7A
____Light off? See 7B

___7A: Faulty ECM terminal "B2" or bad ECM.
___7B: Repair open circuit 120 to ECM terminal "B2".

*** Oil pressure switch test: Our 2.8's have two oil pressure switches. One is for the
gauge panel to control our oil pressure light (or gauge). The other one will keep the fuel
pump running if the relay happens to die while you're driving. I assume the theory was that
if you pull out onto a highway and the relay dies, you don't get killed? Anyway...

OP1. Start the engine, get it up to normal operating temperature. If you can, verify that
______the oil pressure is normal. Disconnect fuel pump relay- the motor should keep running.

______Engine stops? Bad oil pressure switch.
______Engine keeps going? See "OP2"

OP2. Reconnect fuel pump relay. Ignition "off". Find the fuel pump test terminal on the
______ALDL (Assembly Line Diagnostic Link, the connector above the driver's feet you used
______to get the error code out), which is terminal "G" -- the bottom leftmost terminal.
______Probe that terminal "G" with a test light to ground.

______Light off? No trouble found! (Doubtful...)
______Light on? Bad oil pressure switch. Oh yeah this switch is screwed into your engine
_________________block, right above your oil filter, with an orange and a tan/white wiring
_________________harness on it.

Whew.

-Tom P (Hot rodded 1986 Firebird 2.8l)


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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!

[This message has been edited by TomP (edited January 23, 2001).]

 

Get 'em Tom! Rest those fingers in ice for a while!

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My only mod: Flowmaster 40 series