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P1233/p1235 grand Marquis plus AC issue

12K views 12 replies 4 participants last post by  CatSkinner 
#1 ·
So my brother recently took his car to a 2bay mechanic shop because his AC was not cooling. Long story short I ended up towing the car home and troubleshooting it myself. They claimed the car died off on its own while troubleshooting the AC and never restarted. However when I got it home I found the fuel pump fuse missing. I replaced it and the car started back up. I saw that it had a CEL so I read the code and it was p1233. Reset it and the next day while he came to my house I topped of his AC.

I go to test drive the car and while driving the car back and making a turn the car just dies. Try to start it several times and it does not fire. We push it half a block up and read the codes again it shows p1233 and now a pending p1235. However I crank the car and it restarts, only this time I can hear something in the trunk (fuel pump?) Chatter for half a second after start up. Restart one more time and the same thing happens.

I know the "shop" was pulling fuses and relays left and right because they couldn't get the car to start. They replaced several relays with used ones because they "tested bad" but the car never started. Fuse #6 and relay #203 are there. I'm hoping it's just a bad used relay but I came here for an opinion. As far as I take it those error codes are related to the circuit for the fuel pump meaning that the fuel pump itself isn't the issue?

I also have another AC issue but I guess that's not important now.
 
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#4 ·
P1233
Description
Fuel System Disabled or Offline Conditions
Cause
Key on or engine running and the PCM did not receive duty cycle signals from the FPDM

P1235
Description
Fuel Pump Control Out of Range Conditions
Cause
Key on or engine running, then the PCM received a signal (on FPM over SCP bus) that the FPDM that it had received an invalid or missing fuel pump circuit
 
#5 ·
Most common problems for P1233 is either the inertia switch or the relay. Electrically disconnect the pump and jump the relay to see if you get power at the connection (also verify the inertia switch isn't tripped). If you have power, check your ground.
 
#6 ·
Ok so remember in the beginning of the post i said that the shop was pulling relays left and right trying to get the car to start? The car wouldnt start at the shop because it was missing fuse #6 for the fuel pump. They claimed they did not do anything as they said the car died on its own behalf. I do not know if thats a lie, because It had to arrive at the shop with the damn fuse in place because otherwise the car wont start.

In the process of trying to get the car to start at the shop, they removed 4 out of the 5 original micro relays and replaced them with used units they had laying around, some are unbranded, one is toyota and the other is jaguar. Anywho, i removed the (brown) relay #203 for the fuel pump and switched it with the (black) relay #201 for the horn. When i did that the car started fine but the horn stopped working. I retested by swapping them again, although the car started with brown relay im assuming it was just using fuel already in the fuel rail and im assuming it wouldve cut out later.

So to make things short:
Horn works with black relay but not the brown one. The car has died so far with the brown relay only, in the fuel pump slot. I asked my brother to continue to test the car with the black relay in the fuel pump slot. Heres hoping that will take care of the issue. Im ordering a new relay online meanwhile just for peace of mind that the "good-used" relay will be replaced with a 100% good new relay.

We checked the inertia switch several times while in shop and at home and it has always been depressed, not sprung out.
 
#8 ·
I would go back to the shop and make them replace the relay while giving them an earful. Its rediculous how they lied about it dying while running but clearly it hadnt. They blatently lied. Its that kind of stuff that really angers me and the reason I dont take my cars to shops.

Anyway now that my composure has returned, whats going on with the ac or did you fix it when you topped it off?
 
#9 ·
@baja
When the car wouldn't start at the shop it had 0 pressure at the fuel rail (missing fuse). When I got it home and put the fuse in then the car started fine, meaning it had fuel pressure. When the car died while driving the next day we pushed it about 1/8 mile back to my home. It didn't occur to me to push the shcrader when it died s we were in the middle of the street and a few hundred feet from my house. But when we got to my home I tried restarting the car and it hesitantly started right u and stayed running. Trunked it off and on and stayed running. Since my brother was at my house he decided to just take it home before it died again. The next day he tried to take it to work only to have it die again. He left it at an AutoZone and when I went there in the afternoon, without doing anything else I simply swapped the fuel pump relay and it started right up. Drove it back to his house and that's when we tested several times with the horn relay swap.

@vic
The reason he took his car to the unknown mechanic was because he said his AC had gradually gotten hotter and hotter. My brother told me that they were trying to manually power the compressor??? When he drove it to my house however the clutch was cycling just fine. Only took low pressure and it was reading about 21 psi on engagement. I filled it with 10 or so oz of r34 bringing the pressure up to around 36psi but it just made the vents come out hotter almost as if the heaters were on.

I did the self test on the climate control and it only comes up with code 024 (actuator door?). I remember I rebuilt the little o rings behind the unit about a year ago. At the time he wasn't getting enough air through the main vents.
 
#11 ·
Good luck and let us know what you find. BTW, I just replaced the AC compressor in my son's Mustang because the system was loosing pressure and the leak could not be found (?) Once the compressor was out I was able to find the leak behind the clutch, but it was almost impossible to see even with a black light and dye in the system. I replaced the compressor and it has held pressure for over six months now. However, if the system is holding pressure and it's the blend door in your Bro's car that's causing the problem, then that's another issue altogether (that's profound, sorry, haven't had coffee yet)
 
#12 ·
Would the blend door make it come out hot when I cycle the AC on?. Without the AC on it just comes out room temp (100F or so- Az), with it it blows hot. I know he told me the heat never worked during winter. Assuming the blend door broke at that position, shouldn't it be blocking the heat side if it is in fact the blend door causing it?
 
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