Dtc 524

N

Neil

Registered
Hello LOD

I've been with you guys for 5 years and 2 gen 1's but I just joined recently. You all have been a great help! So here's my trouble. When I'm accelerating hard (just to get on the express way because I have to) I get a MIL. Code 524 shows either low or high speed fuel pump output so it must be the high speed. The manual lists 3 possible causes. Open in power-to-pump
circuit between the VCRM and FPM splice. Open in B(+) supply to VCRM (pins 4+5). Or left HO2S short to power. I also get DTC 173 but that's for the right HO2S indicates lean. I know I'll have to get out my meter and start testing but I thought I'd see if others have had this trouble first. Thank's for all your help!
 
****MOVE TO DRIVETRAIN*****

Sup Neil! Welcome!

I'm going with you have a Gen 1(year/model helps). Here is what AllData has to say!

DTC 524
Low speed fuel pump circuit open (battery to powertrain control module).

XB135 - KOEO Code 524/543: Is Continuous Code 583 Present???

Key On Engine Off Diagnostic Trouble Codes (DTC) 524/543 indicate that when the Powertrain Control Module (PCM) commanded the fuel pump on, voltage was not detected on Fuel Pump Monitor (FPM) , (PCM Pin 8). Although DTC 524 refers to the low speed output (Variable Control Relay Module (VCRM) Pin 24) and DTC 543 refers to the high speed output, it is not possible to distinguish between circuits due to the vehicle wiring and fuel pump operating strategy

Possible causes are:

Without DTC 583:
Open in power-to-pump circuit between VCRM and FPM splice.
Open in B(+) supply to VCRM (Pins 4 and 5).
Left Heated Oxygen Sensor (HO2S) short to power.


With DTC 583:
Power-to-pump/FPM circuit short to ground.

Is Continuous Memory DTC 583 present?

***************
Is it? :)

I'm guessing NO so here you go........

XB144 - Does Engine Start With HFP Relay Disconnected

Key "OFF".
Disconnect High Speed Fuel Pump (HFP) relay (located in Power Distribution Box).

Attempt to start engine and run for one minute.
Does the engine start and run for one minute?

************
This is you lesson for today my son....... Let us know what happends.
 
Hey J,
Thank's for the advice. I'll pull that relay and let you know what happens. I've got a wife, kids and a job that keep cutting into my car time!
Neil
 
OK I found that relay. The owners manual fuse box schedule just calls it fuel pump relay but shop manual calls it high speed fuel pump relay. It's the last one in a line of five relays closest to rear of car. I pulled it and started the car. It ran for for a couple of minutes without trouble. So what does that mean? Thanks for your help!
Neil
 
Just my two cents here, but an electronic problem wouldn't normally occur only at high rpms...unless your alternator is bad.

My knee-jerk guess would be a bad fuel pump, since those things commonly tend to die on our cars. Could also be a clogged fuel filter, though you wouldn't get a fuel pump code for that. Your O2 sensor would read lean because the engine isn't getting the fuel it needs.

I could be wrong though, and the diagnostics you're doing couldn't hurt. You'll eventually find what the issue really is.
 
XB127 - Check Left HO2S For Short to Power

NOTE: Due to the internal circuitry of the Powertrain Control Module (PCM) , a left Heated Oxygen Sensor (HO2S) signal short to power could produce Diagnostic Trouble Codes (DTC) 524, 542, 543.

Key "OFF".

Disconnect left HO2S.
41933935.gif

Measure resistance between HO2S signal pin and key power pin at the HO2S connector.

Is resistance greater than 10,000 ohms?

Yes -- Go to XB128. See: XB128 - Check Left HO2S Circuit For Short to Power
No -- Replace left HO2S.

***********
XB128 - Check Left HO2S Circuit For Short to Power
Notes

Key "OFF".

Left Heated Oxygen Sensor (HO2S) disconnected.

Disconnect Powertrain Control Module (PCM) . Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary.

Key "ON".
41933936.gif

Measure voltage between the HO2S signal at the HO2S vehicle harness connector and the battery negative post.

Key "OFF".

Was voltage less than 2.0 volts?

Yes -- Replace PCM. Reconnect all components. Rerun quick test. See: Displaying & Reading Trouble Codes\Quick Test Appendix (Detailed Testing Instructions)
No -- Service left HO2S circuit short to power.

Thats it.........if you DID NOT have the 583 code than you will find one of these being your problem.

Logres....if you have a wire that is breaking down or has a bad/corroded connection, you're going to have more of a problem at higher rpms because its drawing more amps vs low rpms where the current can pass because the load in minute. Just like a spark plug wire that fails when under a load....more power required and the circuit fails. I do agree that a lot of electrical problems will show face with a bad alternator at higher rpms(more load/draw) but your theory of electrical probs not normally occuring at high rpms kinda doesn't make sense when it relates, for example, to fuel pump drawing more power at a higher rpm but not having the voltage to push it(i.e. high speed FP output). Thats my two cents :)
 
J said:
Logres....if you have a wire that is breaking down or has a bad/corroded connection, you're going to have more of a problem at higher rpms because its drawing more amps vs low rpms where the current can pass because the load in minute. Just like a spark plug wire that fails when under a load....more power required and the circuit fails. I do agree that a lot of electrical problems will show face with a bad alternator at higher rpms(more load/draw) but your theory of electrical probs not normally occuring at high rpms kinda doesn't make sense when it relates, for example, to fuel pump drawing more power at a higher rpm but not having the voltage to push it(i.e. high speed FP output). Thats my two cents :)
Click to expand...

I hear ya on the spark plug example, but does the fuel pump really draw that much more power under load? And certainly not at 10,000+ volts like the plug wires. That's why they will end up arcing...
 
logres said:
I hear ya on the spark plug example, but does the fuel pump really draw that much more power under load? And certainly not at 10,000+ volts like the plug wires. That's why they will end up arcing...
Click to expand...

I don't know about specific fuel pump load, but any load on any pump is dependant upon delivered volume and pressure. So yes, if a higher demand means more volume and/or pressure, the power required by the pump will be higher.
 
driller said:
I don't know about specific fuel pump load, but any load on any pump is dependant upon delivered volume and pressure. So yes, if a higher demand means more volume and/or pressure, the power required by the pump will be higher.
Click to expand...


Thats what I'm trying to say :). A variable fuel pump runs at different power levels...WOT needs MAX pressure, which in turn needs MAX voltage to run it. Bad connection on the fuel pump or a smashed/cut wire somewhere will cause the voltage to find a different conductor or ground out somewhere, or just supply 8 volts when it needs 12 volts.

Ofcourse the spark plug wire example is different, but it was just an analogy.

Look at the AllData info I posted....EVERYTHING is surounded around an electrical fault, and if the light comes on at higher loads, theres your proof.

Open in power-to-pump circuit between VCRM and FPM splice.
Open in B(+) supply to VCRM (Pins 4 and 5).
Left Heated Oxygen Sensor (HO2S) short to power.
 
J said:
Look at the AllData info I posted....EVERYTHING is surounded around an electrical fault, and if the light comes on at higher loads, theres your proof.

Open in power-to-pump circuit between VCRM and FPM splice.
Open in B(+) supply to VCRM (Pins 4 and 5).
Left Heated Oxygen Sensor (HO2S) short to power.
Click to expand...

Ahhh...I see.

I've only got minor experience with all things electrical.
 
Thanks for the AllData info. That will help me very much. I'm having trouble posting so I hope this works!
 
I replaced the fuel pump with a quality(expensive) aftermarket one 2 summers ago so I don't think thats the trouble. I don't seem to starve for gas when I push it hard. I don't know if the low speed pump is just keeping up with demand or if high is really working.
 
Posting seems to work better if I keep it short. I'll try testing at the left
HO2S and I'll let you know what I find. Thanks again!
Neil
 
logres said:
I've only got minor experience with all things electrical.
Click to expand...

Just so you know I wasn't trying to be argumentive, just pointing out facts :) My goal is to help everyone learn and try not to sound like a know-it-all(which I do a lot :embarrassed: )

Thus is why I used the plug wire analogy....same principle really simple to understand, its just put to use differently.
 
J said:
Just so you know I wasn't trying to be argumentive, just pointing out facts :) My goal is to help everyone learn and try not to sound like a know-it-all(which I do a lot :embarrassed: )

Thus is why I used the plug wire analogy....same principle really simple to understand, its just put to use differently.
Click to expand...

No problem...we're good. Your posts have provided me with a wealth of information as well.
 
Ok good....I know my posts can be "pushy"(been a problem in the past) so I apologize ahead of time. Plus when were typing, there is NO way to tell the other persons emotions....so I try to make as much use of the smileys as possible. :love-it:
 
Hello again friends,
I have not checked my left ho2s yet. I've been dealing with some other possibly related issues. A few months ago I had a radiator leak so I put in a new one and a new thermostat. Then it started running very hot. I tried the old burping at the crossover tube thing( I'm getting good at that) many times and still was running hot. I replaced the water pump on a long shot since it's cheap and easy to install. Still hot. Friends were saying the new stat was bad but I was avoiding that because its not that easy to get at! So I bought another new one and boiled it on the stove to watch it open. I installed it and am running much cooler now! I boiled the old one and it only opened an eighth of an inch! But.... Neil
 
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