Engine New to Mustangs, guidance needed on fault codes 47 & 45


Apr 9, 2021
Hello. I'm Jon or Suds. First post here at Stangnet and completely new to the Foxbodys.

Quick back ground:
We purchased a 1989 hatch foxbody gt AOD transmission apparently converted from a 4cyl LX. A 5.0 was installed and I believe it's from a 91 model. Honestly they did an awesome job imo. After a few things we've done so far, car runs extremely smooth with a few hiccups.

Before I get to the things we've done I'll present the problem.

Using an Innova scan tool and after a 5 or 6 mile run we've have fault code 5, 47,4, and 45 (in that order) at KOER. Also the scanner did NOT show the number of cylinders.

While we've used the new scan tool multiple times to troubleshoot other issues it has always read the cylinders.

I've scanned the net on the codes 47 and 45, we haven't found any help on these. KOEO codes we have is o85 and c96.

Now for the progress so far:
Brand new fuel related parts from CJ Pony
Fuel pump
Filler neck

Fuel filter twice
Fuel rail flushed
Fuel pressure regulator

Injectors in the car were a, I guess you'd call it a single spray plunger type. We bought a set of rebuilt 4 hole spray pattern from a dude in Cali.

Fuel pressure holds 30+ at idle, up to 40 on acceleration.

Compression is 130+

Advanced Auto distributor with tfi.
New plugs
Ford Racing plug wires
Ignition coil
New starter
Battery cables, positive cable to the starter and negative cable.
Fuel pump relay (under driver seat)
Ecc relay
Coolant temp sensor not the one for the gauge cluster
Air charge Temp sensor

Water pump
Thermostat and housing
Intake gasket

Timing is set to 10* with out spout connector

The latest major problem we had possibly solved was the car randomly jerking like the rear end was about to fall out and losing all power when giving it fuel while cruising. Code 18 was popping up every once in awhile that's why we replaced alot of the ignition parts. Distributor and 2 TFIs not to mention tracing wires until I was about to pull the trigger on a new harness. Turned out to be a wire loom that went to the transmission sitting on the exhaust pipe.

I'm not sure what the sensor is that the harness went to, believe it was a neutral safety switch. I only see 2 places a harness runs to, one in the front of the transmission near the bellhousing and the speed sensor next to the cable. The wires weren't visually damaged but the loom conduit was melted a bit. I think the heat from the exhaust pipe was causing some interference some how. Rerouted the loom and cable, no more violent bucks or jerks.

Another note, there is not a charcoal canister, holes in the heads for smog pipes are plugged, both vacuum lines are plugged. Bypass pulley is installed. Connector for the pump is just lying there. Noticed the tail pipe branch is plugged aswell.

This car is pretty much for my son who has zero interest in anything other than cars and video games. Fishing, camping, boating, and hiking too but those aren't things we can do after a hard days work or school. Complete restore on this ride if we have too.

My apologies for a long post, feel free to skip around, I won't mind repeating things if questions are asked. Cheers.
  • Sponsors (?)

Those are not valid codes. There are no single digit codes on eec-iv. They should all be 2-digit codes. Code 47 is a very odd code for Mustangs so I would double check these mixed in with the single digit codes

Code 85 is charcoal canister purge valve

Code 96 is fuel pump circuit. There’s a wire to the ECU that monitors the fuel pump relay. If the relay dies it triggers this code. Often times in mass air swaps this wire is missing. You don’t know how this was wired given that it’s a swap right? You can either run the wire to eliminate the code (if this is the case) or just ignore it.
Last edited:
  • Like
Reactions: 1 user
The 45 & 47 codes are codes that I haven't seen on Stangnet in the last 20+ years that I have been here... They may be spurious codes that didn't get read properly when the codes dumped.

Code 45 - (engine running) Electronic Ignition – coil primary circuit failure – Ignition Systems. Check ignition coil, coil low voltage wiring and TFI module

Code 47 - measured airflow low at base idle. Dirty MAF sensor, obstructed air inlet to MAF sensor, bad MAF sensor. If you have a Cold Air Intake, try rotating the MAF sensor housing (clocking the MAF).

A problem with the neutral safety switch should have given a code 67.
Code 67
Revised 18-Mar-2017 to include warning about the necessity of having a 5 speed O2 Sensor wiring harness when bypassing the wiring for test purposes

Cause of problem:
Clutch not depressed (5 speed) or car not in neutral (5 speed and auto) or not in park (auto) or A/C in On position when codes where dumped. Possible neutral safety switch or wiring problem. This code will prevent you from running the Key On Engine Running tests.

External evidence from other sources claims that a code 67 can cause an idle surge condition. Do try to find and fix any issues with the switch and wiring if you get a code 67.

What the NSS (Neutral Safety Switch) does:
5 speed transmission: It has no connection with the starter, and the engine can be cranked without it being connected.
Auto transmission: It is the safety interlock that prevents the starter from cranking the engine with the transmission in gear.
What it does for both 5 speed and auto transmission cars:
The computer wants to make sure the A/C is off due to the added load on the engine for the engine running computer diagnostic tests. It also checks to see that the transmission is in Neutral (5 speed and auto transmission) and the clutch depressed (T5, T56, Tremec 3550 & TKO)). This prevents the diagnostics from being run when the car is driven. Key On Engine Running test mode takes the throttle control away from the driver for several tests. This could prove hazardous if the computer was jumpered into test mode and then driven.

The following is for 5 speed cars only. Do not do this unless you are sure that you have a 5 speed O2 Sensor harness!!!! Smoke, sparks and expensive pain in the wallet may ensue if you don’t.
The NSS code 67 can be bypassed for testing. You will need to temporarily ground computer pin 30 to the chassis. Computer pin 30 uses a Lt blue/yellow wire. Remove the passenger side kick panel and then remove the plastic cover from the computer wiring connector. Use a safety pin to probe the connector from the rear. Jumper the safety pin to the ground near the computer.
Be sure to remove the jumper BEFORE attempting to drive the car!!!

Computer wiring harness connector, wire side

Code 85 CANP solenoid - The Carbon Canister solenoid is inoperative or missing.

Revised 11 –Jan_2015 to add warning about vacuum leaks due to deteriorated hose or missing caps on vacuum lines when the solenoid is removed.

Check vacuum lines for leaks and cracks. Check electrical wiring for loose connections, damaged wiring and insulation. Check solenoid valve operation by grounding the gray/yellow wire to the solenoid and blowing through it.
The computer provides the ground for the solenoid. The red wire to the solenoid is always energized any time the ignition switch is in the run position.

If you disconnected the carbon canister and failed to properly cap the vacuum line coming from under the upper intake manifold, you will have problems. You will also have problems if the remaining hose coming from under the upper intake manifold or caps for the vacuum line are sucking air.

Charcoal canister plumbing - one 3/8" tube from the bottom of the upper manifold to the rubber hose. Rubber hose connects to one side of the canister solenoid valve. Other side of the solenoid valve connects to one side of the canister. The other side of the canister connects to a rubber hose that connects to a line that goes all the way back to the gas tank. There is an electrical connector coming from the passenger side injector harness near #1 injector that plugs into the canister solenoid valve. It's purpose is to vent the gas tank. The solenoid valve opens at cruse to provide some extra fuel. The canister is normally mounted on the passenger side frame rail near the smog pump pulley.

Connecting the gas tank vent line directly to the intake manifold will result in fuel vapor being constantly sucked into the intake manifold. There is unmetered fuel that the computer cannot adjust for. The result is poor idle and poor fuel economy.


It does not weigh but a pound or so and helps richen up the cruse mixture. It draws no HP & keeps the car from smelling like gasoline in a closed garage. So with all these good things and no bad ones, why not hook it up & use it?

The purge valve solenoid connector is a dangling wire that is near the ECT sensor and oil filler on the passenger side rocker cover. The actual solenoid valve is down next to the carbon canister. There is about 12"-16" of wire that runs parallel to the canister vent hose that comes off the bottom side of the upper intake manifold. That hose connects one port of the solenoid valve; the other port connects to the carbon canister.

The purge valve solenoid should be available at your local auto parts store.

Purge valve solenoid:

Code 96 for 86-90 model 5.0 Mustang – KOEO- Fuel pump monitor circuit shows no power - Fuel pump relay or battery power feed was open - Power / Fuel Pump Circuits. The fuel pump lost power at some time while the ignition switch was in the run position. The main power feed to the pump is what is losing power.

Look for a failing fuel pump relay, bad connections or broken wiring. The fuel pump relay is located under the passenger seat. On Mass Air Conversions, the signal lead that tells the computer that the fuel pump has power may not have been wired correctly.
See http://www.stangnet.com/tech/maf/massairconversion.html

Look for power at the fuel pump - the fuel pump has a connector at the rear of the car with a pink/black wire and a black wire that goes to the fuel pump. The pink/black wire should be hot when the test connector is jumpered to the test position. . To trick the fuel pump into running, find the ECC test connector and jump the connector in the lower RH corner to ground.


86-90 Models:
Using the diagram, check the red/black wire from the fuel pump relay: you should see 12 volts or so. If not, check the inertia switch: on a hatch it is on the drivers side by the taillight. Look for a black rubber plug that pops out: if you don't find it, then loosen up the plastic trim. Check for voltage on both sides of the switch. If there is voltage on both sides, then check the Pink/black wire on the fuel pump relay: it is the power feed to the fuel pump. Good voltage there, then the fuel pump body to tank wiring harness connector is the likely culprit since it is getting power. No voltage there, check the Orange/Lt blue wire, it is the power feed to the fuel pump relay & has a fuse link in it. Good voltage there & at the Pink/black wire, swap the relay.

Keep in mind that the relay wiring and socket can also cause intermittent problems. Clean the relay socket with non-flammable brake parts cleaner or electrical contact cleaner. If you find damaged wiring at the relay socket, replacement pigtail socket assemblies are available at the auto parts stores. Be sure to solder the wires and cover the solder joints with heat shrink tubing if you replace the relay socket.

Last edited:
  • Like
Reactions: 1 user
You don’t know how this was wired given that it’s a swap right? You can either run the wire to eliminate the code (if this is the case) or just ignore it.
Correct. I have no clue how it's wired. PO seemed to have labeled everything prior to removal. Honestly we had no idea this was done until we decided to purchase the car. The undercarriage looked extremely good so went through with the purchase.

I do believe we have major wiring issues. I believe the ecm is a A9L with a factory harness. It's very difficult to see that it was once an 4 cylinder LX. Even has the air bag with steering wheel controls. Seems like I've heard someone says 89 LXs did not have that.
Check the VIN Code - your auto insurance agent will be glad to inform you.
Or just use Google to look up the Vin Code definitions
I knew the swap was done before purchasing. This was a cheap "barn find". It sat in a garage for maybe 10 years. PO had intentions on making a drag car out of it. They pretty much started prepping it for paint before it was parked. It's a nice project for my son and I.

I have to be honest and say I don't know much at all about mustangs. Hell, I didn't know anything about a diesel until I bought one.
I haven't found any hack jobs on the harness at all. I believe the problems are how the harness is ran. Pinched wires, wire loom sitting on extremely heated areas (came across that), stressed wires. Most of the tape-on clips that hold the loom are either missing and/or I don't know where they go.
Yeah, that pump and hanger look wasted, that injector looks crusty too.
Have you/are you going to pull the dash to make sure the wires there are ok?
I found a box full of those wiring retainers on line, much cheaper than the 5 or 10 packs you can buy, there are a sht ton of them and they are all old and brittle.
As for how the car was born ...

The 5th,6th and 7th digits in the VIN give body and trim type. You said it is a hatch so it should be one of the following:

P41 - LX hatch
P42 - GT hatch

The next digit gives the factory engine:
A - 2.3L 4 cylinder
E - 5.0L 8 cylinder

What is the max rpm on the factory tach? 4 cylinder cars go to 6k, 8 cylinders go to 7k. Using a 4 cylinder tach on a V8 will show twice as many revs as actual. If you have a V8 tach, chances are the gauge cluster was switched and odometer reading may not be actual for the car.

No, you wouldn't want the RX7, then you get an oil burning Wankel
  • Like
Reactions: 1 user
Right now I'm focusing on the koeo 96 code.

Just ohm test all the wires from the fuel pump relay. All wires test below 0.3. I'm assuming that means no breaks in the wire and all wires are good.

I did not drop the tank to test the wires from the inertia switch to the pump. Just probed the wires at boot.