check engine light with a 543 176 177codes

[GUY L]

i have a 95 sho with 96000 miles and when it is cold it runs great but as soon as it heatsup it runs like crap the check engine light comes on and its like the car is bogging down when i start from a dead stop and just start off driving its like it is starving for fuel but if i really step on the gas it dosent bog. the 543 code means fuelpump pressure circut open and 176 177 mean bank 1 lean bank 2 rich. if anybody knows about this i could really use some help. thanks

 

[Slo-Sho]

Replace BOTH of your Oxygen sensor's. I suspect your fuel mileage isn't so great either? When your SHO is cold the EEC runs in "open loop" mode until the car warms up, meaning that it runs on pre-programmed fuel and spark tables. The 543 code you got, fuel pump secondary circuit failure, just means your car stalled with the ignition still on. Nothing to worry about.

 

[sdpatt]

Actually, the O2 sensor codes are as follows:

176 (M) Oxygen sensor not switching - system is or was lean Left or Front HO2S - Fuel control

177 (M) Oxygen sensor not switching - system was rich Left or Front HO2S - Fuel control

Both of those codes refer to the front bank and its sensor. That is good because if both banks were having problems it could be a fuel mixture or vacuum leak problem. I do agree that you should replace both sensors. They should be changed at the same interval as the spark plugs - 60,000 miles. I recommend the following sensors from AutoZone.

3.0L Bosch 13942 $38.99
3.2L Bosch 15716 $49.00

 

[Markus]

slosho:
The 543 code you got, fuel pump secondary circuit failure, just means your car stalled with the ignition still on. Nothing to worry about.

Not necessarily. Bad O2 sensors will also trigger this code.

 

[sdpatt]

Markus:

slosho:
The 543 code you got, fuel pump secondary circuit failure, just means your car stalled with the ignition still on. Nothing to worry about.

Not necessarily. Bad O2 sensors will also trigger this code.

No, I don't believe that they will. Completely independent circuits with separate circuits for the error code triggers.

 

[Markus]

sdpatt:

Markus:

slosho:
The 543 code you got, fuel pump secondary circuit failure, just means your car stalled with the ignition still on. Nothing to worry about.

Not necessarily. Bad O2 sensors will also trigger this code.

No, I don't believe that they will. Completely independent circuits with separate circuits for the error code triggers.

I just did the following test:
1) Warmed up engine and made sure computer had no codes. Let engine cool.
2) Disconnect front O2 sensor when engine cold
3) Drove till engine warmed up and CEL came on
4) Got codes: 176, 177, 543

The engine never stalled

From the Ford manuals:

543 Hard code - goto X90
543 Memory code - goto X110

From X90:
Diagnostic Trouble Code (DTC) 543/524 indicates a fuel pump secondary circuit failure between the B(+) supply and the Fuel Pump Monitor (FPM) connection to the power-to-pump circuit.Possible causes:

No Starts:
· Open circuit between the B(+) supply and the FPM connection to the power-to-pump circuit.
· Fuel pump relay contacts always open.

Engine Starts:
· Left/Front Heated Oxygen Sensor (HO2S) short to power
· Damaged Powertrain Control Module (PCM).

X110 also says 543 can be generated by a faulty O2 sensor

<small>[ September 08, 2002, 04:44 PM: Message edited by: Markus ]</small>

 

[sdpatt]

That's more information than I have. Was the original 543 code a memory code? How did you "Warmed up engine and made sure computer had no codes?" To clear the memory codes you must install the jumper, run the test and remove the jumper during the code display.

 

[Markus]

sdpatt:
That's more information than I have. Was the original 543 code a memory code? How did you "Warmed up engine and made sure computer had no codes?" To clear the memory codes you must install the jumper, run the test and remove the jumper during the code display.

I drove the car 'till it was at operating temperature. Parked the car and ran both KOEO and KOER tests - only codes were 111. Reran the KOEO codes and while the PCM was spitting out 111 I removed the jumper.

I let the car cool down for an hour or so and then disconnected the front O2 sensor, went for a short drive, got a CEL on, and re-ran the KOEO test.

 

[road92]

I have a 1993 SHO ATX with the same problems. I get a 543 while doing the KOEO test (When the car doesn't start after its warm) I also get a C.E light after driving at highway speed for about 10 minutes which translates to a 176 code. After looking at previous posts I'm confused at the responses. Could a bad O2 sensor cause this whole mess?? or are they seperate problems?? Thanks in advance.

Road92
Stock 93 ATX @163,000 clicks

 

[Markus]

road92:
I have a 1993 SHO ATX with the same problems. I get a 543 while doing the KOEO test (When the car doesn't start after its warm) I also get a C.E light after driving at highway speed for about 10 minutes which translates to a 176 code. After looking at previous posts I'm confused at the responses. Could a bad O2 sensor cause this whole mess?? or are they seperate problems?? Thanks in advance.

Road92
Stock 93 ATX @163,000 clicks

I suspect your 543 code was triggered by a bad O2 sensor. Replace the sensor, clear the codes, and drive. If you subsequently get a 543 without 176/177 then there is a fuel pump problem.

 

[road92]

Mark, I just ordered two O2 sensors from AutoZone. I should have them in a couple of days, I'll let you know how I come out. Thanks again.

Road92

 

[road92]

Thanks guys, I replaced both O2 sensors and my problems are gone for now thumbs_u . No more 176 codes after driving for about 10 minutes and no more KOEO Code 543 failures with starting after it was warmed up.

You definitely can not own one of these without the help of all you guys helping with diagnostics.

Thanks again.

Road92
Stock Red 93 ATX 164,000 clicks and no C.E light for the last 100 miles!!!

<small>[ September 30, 2002, 10:25 PM: Message edited by: road92 ]</small>