Retrieving the Codes The easiest way to retrieve diagnostic trouble codes on a Ford is with a scan tool. Fords require opening and closing the self test input (STI) lead at various times; scan tools have much of the diagnostic routine programmed in, and will provide any prompts necessary to walk you through the test procedure.

What’s more, many Fords don’t provide a malfunction indicator lamp to flash out the codes. Very often you have to use an analog voltmeter or some other type of device to read the codes.

Finally, later model× Fords use three-digit codes; counting the flashes or voltmeter needle sweeps for code "675" (transmission range sensor voltage out of range) can become awkward at best.

Using a meter to read code 12 isn't too bad, but code 675 could offer a bit of a problem.

But if a scan tool isn’t available, you can read× Ford diagnostic trouble codes without one, using the malfunction indicator lamp (if there is one) or a voltmeter.

Start by locating the self test connector: It’s usually around a shock tower or near the firewall.

The self test connector is actually two connectors: a main connector and a separate pigtail connector. Here’s how to identify the individual terminals:

The self test input lets you tell the computer to display the codes; the self test output lets you read them.

With the key off, ground the self test input connector—that’s the separate pigtail connector. If the car has a malfunction indicator lamp, that’s all you have to do—turn the key on, engine off, and the lamp will start flashing codes.

Grounding the self test input terminal puts the computer system into self test mode.

If the vehicle has a malfunction indicator lamp, it'll provide diagnostic trouble codes.

But if there’s no malfunction indicator lamp in the car, you’ll need to use something to read the codes. Ford recommends an analog voltmeter for this, but you can use almost anything that displays voltage changes: A digital oscilloscope, test light, or even a beeper will all work to display the codes. We’ll use a voltmeter, but feel free to substitute.

Connect the negative lead of your voltmeter to the self test output terminal. Connect the positive lead to any 12-volt source, such as the positive battery terminal.

If the car doesn't have a malfunction indicator lamp,you can read the diagnostic trouble codes with an analog voltmenter.

Counting the Codes Now turn the key on, engine off, and the voltmeter needle should start sweeping toward 12 volts.

The time between the flashes or needle sweeps lets you determine whether it’s part of the same digit, a different digit, or a different code. Here’s how to identify the difference:

• There’s a 1/2-second separation between flashes or sweeps in a digit. • There’s a 2-second separation between digits. • There’s a 4-second separation between codes.

So here’s how a series of codes will appear:

Here's how to read the codes, base on the on-time and the off-time.

Reading the Codes Fords display three different types of codes: Two are key on, engine off (KOEO) codes; that is, to read these codes, the key must be on, but the engine off. The other is a key on, engine running (KOER) code. Here are the three different types of codes:

• KOEO On-Demand • KOEO Continuous Memory • KOER On-Demand

Here’s how to read each code:

On vehicles with diesel engines, you must hold the accelerator pedal to the floor during the KOEO On-Demand and× Memory tests.

KOEO On-Demand Codes: These are the first codes the computer displays during a self test. KOEO On-Demand codes aren’t stored in memory; the computer runs through a quick series of checks, and indicates any problems it recognizes at that moment. If the problem isn’t there right now, it won’t show up during this series. Any codes that display during this series indicate hard faults.

If doesn’t recognize any faults in the system, the computer displays code 11 (or 111 on systems with three-digit codes). This is also called "Pass 11" (or "Pass 111"); it indicates no hard faults in the system.

Separator Code: In between the KOEO On-Demand codes and the KOEO Continuous Memory codes, the system displays a code 10. This appears as a single flash (or sweep), since the computer can’t display a zero. Code 10 tells you there are no more KOEO On-Demand codes in memory, and it’s time to move on to the KOEO Continuous Memory codes. There’s a 6 – 9 second pause before and after separator code 10.

KOEO Continuous Memory Codes: These are the next series of codes; they’re the codes the computer has stored in memory. While they may indicate a problem that’s there now, they may also indicate intermittent failures, or a failure that only appears when the engine’s running, such as a vacuum leak.

If there are no codes in memory, the computer again displays a "Pass 11" (or "Pass 111") code.

If you’re using a scan tool, you may have to wait up to 15 seconds for the system to display its× Continuous memory codes. Give it time: If you disconnect the scan tool before it’s finished displaying the codes, the system will erase the codes before you have a chance to read them.

KOER On-Demand Codes: Once you’ve read the KOEO On-Demand and Continuous Memory codes, your next step is to check for problems that only show up while the engine’s running. These problems appear as KOER On-Demand codes. Since they’re on-demand codes, they don’t store in memory. And they indicate problems that only show up when the engine’s running.

For example, a vacuum leak to the MAP sensor may affect transmission operation, but it won’t show up during the× Memory codes. And since there’s no vacuum when the engine’s off, it won’t show up during the KOEO self test either.

There are three types of codes Fords provide:KOEO On-Demand Codes, KOEO Continuous Memory Codes, and KOER On-

Demand Codes.

Here’s how to check the KOER On-Demand Codes:

• Disconnect the ground wire from the self test input wire. • Make sure the transmission’s in park; set the emergency brake and block the drive wheels. • Start the engine, and let it reach normal operating temperature. • Shut the engine off. • Ground the self test input wire again. If you were using a voltmeter to display codes, make sure it’s connected. • Restart the engine.

Here’s what you’ll see:

Engine ID Code: The first thing the computer will do is to send the Engine ID code. This code should be a series of pulses, equal to half the number of cylinders in the engine. So a four cylinder engine will receive two pulses, a six cylinder receives three pulses, and an eight cylinder receive four pulses.

Technician Intervention As soon as the system displays the cylinder ID, you’re going to have to perform a few quick procedures:

• Turn the steering wheel at least 1/2 turn… • Press the brake pedal, and… • Cycle the transmission control switch on and off (if equipped).

Now there will be a long pause — maybe as long as 20 seconds.

Dynamic Response Test: At this point, some systems will require a Dynamic Response Test. The computer examines the sensor response when you goose the throttle.

Watch for a single pulse: That’s dynamic response code 10. If you see this single pulse, goose the throttle quickly, all the way to the floor, and release it.

Some systems won’t require a dynamic response test. They’ll skip ahead to the next step.

Now the needle on your voltmeter may wiggle a bit. That’s the computer sending its fast codes; these are the codes a scan tool would read. Ignore them.

Six seconds after the computer delivers its fast codes, it begins pulsing out the KOER On-Demand Codes. Remember, these are the codes that won’t remain in memory; any problem that only shows up while the engine is running should appear in these codes.

If the computer doesn’t identify any problems, it’ll display a Pass 11 code.

Computed Timing Test: You can stop here, but at this point the computer fixes the timing at about 20° before top dead center. This allows you to check the timing, to make sure the computer is controlling it properly.

Power Balance Test: Finally, on vehicles with sequential fuel injection, the system goes into a power balance test. This enables the computer to identify weak cylinders in the engine.

To end this test mode, shut the key off and disconnect the ground lead to the self test input terminal.

The Wiggle Test As One of the biggest problems you’re likely to run into is loose connections. Most manufacturers have a continuous harness, from the computer connector to the inputs and outputs, to prevent connection problems.

Not Ford. Most Fords have dozens of connectors, with short pieces of harness between them. This enables× Ford to use the same harness for many different cars and trucks. But it also presents the possibility of a loose connection causing a computer system problem.

That’s why× Ford builds a special test mode into their computer systems: the wiggle test. The procedure is simple: You put the computer into a special mode, where it looks for momentary glitches, and then wiggle the harness, shake the connectors, tap on sensors and switches. You can even apply heat to components, to see if they have a problem after they get hot.

Ford's wiggle test helps identify loose connections or intermittent failures in components or circuits.

KOEO Wiggle Test There are two types of wiggle test: engine off and engine running. The engine running test actually lets you drive the car, to look for problems that only show up while driving. Here are the procedures for entering and performing the wiggle tests:

• Erase any codes in memory. • Turn the key off. • If you’re using a voltmeter to read the codes, connect it to the self test output terminal and battery positive, the same way you did to read the codes. If you’re using the malfunction indicator lamp, skip to the next step. • Turn the key on, engine off. • Ground, unground, and ground the self test input terminal again (Ford calls this "latch" and "unlatch"). This puts the system into the wiggle test mode.

Ground, unground and ground the self test input terminal again to put the system into the wiggle test mode.

Now work your way around the wiring harness, wiggling the wires and connectors. Tap gently on the sensors and outputs. If you suspect a temperature-related problem, apply heat to the components or connectors with a hair dryer or heat gun.

If the computer sees any problems during this test, the needle on your meter will wiggle slightly. That indicates the computer stored a code in memory. Go back and check the KOEO Continuous Memory codes.

KOER Wiggle Test Another type of wiggle test you can perform is to check the system with the engine running. This "key on, engine running" wiggle test lets you stress the components and circuits under actual driving conditions. So this test can be very useful for isolating hard-to-find component and circuit failures.

Here’s how to perform the KOER wiggle test:

• Erase any codes in memory. • Turn the key off. • If you’re using a voltmeter to read the codes, connect it to the self test output terminal and battery positive, the same way you did to read the codes. If you’re using the malfunction indicator lamp, skip to the next step. • Start the engine. • Ground, unground, and ground the self test input terminal again (Ford calls this "latch" and "unlatch"). This puts the system into the "engine running" wiggle test mode.

Now go for a drive; try to duplicate the conditions that cause the problem in the first place. Hard acceleration, quick deceleration, hard turns — whatever condition seemed to cause the problem. When the problem occurs, the needle on your meter should wiggle slightly; if the vehicle has a MIL, it’ll flash. Check the KOEO Continuous Memory codes to determine the source of the problem.

Output State Test There’s one more test you may want to perform during your Ford diagnostic checks: the output state test. During this test, you can turn nearly all of the computer-controlled solenoids and relays on and off, just by pressing and releasing the gas pedal.

The output state test occurs right after the computer system finishes displaying the KOEO Continuous Memory codes. As soon as the× Memory codes are finished, press the gas pedal to the floor and release it. That puts the system into the output state mode. Nearly all of the computer outputs should be energized — including the transmission shift solenoids.

Now you can check the circuits, to make sure they’re energized, and check the solenoids, to make sure they’re working. This is also a good time to think about Ohm’s Law: Volts ÷ Ohms = Amps. So if you know the solenoid resistance spec, you can determine whether the solenoid is okay by measuring its current draw.

For example, if the solenoid should have 10 ohms resistance, the formula would be:

12.6 ÷ 10 = 1.26

…so the solenoid should be drawing 1.26 amps of current. If the solenoid’s drawing much more than that, it’s probably shorted. If it’s drawing much less, it’s probably open.

The output state test is a great time to put Ohm's Law to work.As long as you know the resistance, you can check the component based on its

current draw.

Press the gas pedal again, and the computer outputs turn off. You can turn the outputs on and off as many times as you want, to determine whether they’re working properly or not.

Clearing the CodesThe procedure for clearing the codes from memory on Fords is simple: Just disconnect the ground lead to the self test input terminal while the system is displaying diagnostic trouble codes. The computer will erase any codes it has stored automatically.

Two-Digit Codes

Three-Digit Codes

Code Description

111 System passed.

112** Air charge temperature sensor or vane air temperature sensor circuit grounded.

113** Air charge temperature sensor or vane air temperature sensor circuit open.

114 Air charge temperature sensor or vane air temperature sensor voltage out of range.

116 Engine temperature sensor voltage out of range.

117** Engine temperature sensor circuit grounded.

118** Engine temperature sensor circuit open.

121 Throttle position sensor voltage out of range or inconsistent with MAF sensor.

122 Throttle position sensor voltage low.

123** Throttle position sensor voltage high.

124** Throttle position sensor voltage higher than expected.

125** Throttle position sensor voltage lower than expected.

126** MAP sensor signal out of range.

128** MAP sensor vacuum hose damaged or disconnected.

129 MAP or mass airflow sensor change insufficient during dynamic response test.

136 Oxygen sensor isn’t switching — indicates lean exhaust, left side.

137 Oxygen sensor isn’t switching — indicates rich exhaust, left side.

139** Oxygen sensor isn’t switching — left side. (’90 vehicles have only one oxygen sensor.)

144** Oxygen sensor isn’t switching — right side. (’90 vehicles have only one oxygen sensor.)

157** Mass airflow sensor voltage below minimum.

158** Mass airflow sensor voltage above maximum.

159 Mass airflow sensor voltage higher or lower than expected.

167 Throttle position change insufficient during dynamic response test.

171** Fuel system at adaptive limit; Right side oxygen sensor isn’t switching. (’90 vehicles have only one oxygen sensor.)

172** Oxygen sensor signal lean — right side. (’90 vehicles have only one oxygen sensor.)

173** Oxygen sensor signal rich — right side. (’90 vehicles have only one oxygen sensor.)

174** Oxygen sensor switching slowly.

175** Fuel system at adaptive limit; Left side oxygen sensor isn’t switching. (’90 vehicles have only one oxygen sensor.)

176** Oxygen sensor signal lean — left side. (’90 vehicles have only one oxygen sensor.)

177** Oxygen sensor signal rich — left side. (’90 vehicles have only one oxygen sensor.)

179** Fuel system at lean adaptive limit at part throttle (exhaust rich).

181** Fuel system at rich adaptive limit at part throttle (exhaust lean).

182** Adaptive fuel lean limit reached at idle.

183** Adaptive fuel rich limit reached at idle.

184** Mass airflow sensor voltage high.

185** Mass airflow sensor voltage low.

186** Vehicles with barometric pressure sensor: Injector pulse width higher than expected.

187** Vehicles with barometric pressure sensor: Injector pulse width lower than expected or mass airflow sensor lower than expected; Vehicles without barometric pressure sensor: Injector pulse width lower or mass airflow sensor higher than expected.

188** Fuel system at lean adaptive limit at part throttle (exhaust rich).

189** Fuel system at rich adaptive limit at part throttle (exhaust lean).

191** Fuel system at lean adaptive limit at idle (exhaust rich).

192 Fuel system at rich adaptive limit at idle (exhaust lean).

193 Flexible fuel sensor circuit failure

211 Profile ignition pickup (PIP) circuit failure.

212 Tach input missing to computer; ignition diagnostic monitor (IDM) input to computer or SPOUT circuit grounded.

213 SPOUT circuit open.

214 Cylinder identification circuit failure.

215** Coil #1 primary circuit failure.

216** Coil #2 primary circuit failure.

217** Coil #3 primary circuit failure.

218** Ignition diagnostic monitor (IDM) signal lost — left side.

219 SPOUT circuit open — spark timing held at 10°.

221 Spark timing error.

222** Ignition diagnostic monitor (IDM) signal lost — right side.

223** Dual plug inhibit control lost.

224** Coil 1, 2, 3 or 4 primary circuit failure.

225 Knock not detected during dynamic response test.

226 Ignition diagnostic monitor (IDM) signal not received.

227 Crankshaft position sensor error.

232** Coil 1, 2, 3 or 4 primary circuit failure.

233 Spark angle pulse width error.

238** Coil #4 primary circuit failure.

239 Crankshaft position signal received with engine off.

241 EDIS to computer ignition diagnostic monitor (IDM) pulse width transmission error.

242 Operating in DIS failure mode.

243 Secondary circuit failure.

311 AIR system wasn’t working during self test — right side with dual oxygen sensors.

312 AIR misdirected during self test.

313 AIR wasn’t bypassed during self test.

314 AIR system wasn’t working during self test — left side with dual oxygen sensors.

326 EGR (EPT/PFE/DPFE) circuit voltage lower than expected.

327** EGR (EGRP/EVP/EPT/PFE/DPFE) circuit below minimum voltage.

328 Exhaust pressure high; EGR (EVP) voltage lower than expected.

332** EGR valve opening not detected by sensor or insufficient EGR flow detected.

334 EGR (EVP) higher than expected with EGR closed.

335 EGR (EPT/PFE/DPFE) sensor voltage out of range during self test.

336 Exhaust pressure high; EGR (EPT/PFE/DPFE) voltage higher than expected.

337** EGR (EGRP/EVP/EPT/PFE/DPFE) circuit voltage too high.

341 Octane adjust service pin in use.

338 Engine coolant temperature lower than expected during the thermostat test.

339 Engine coolant temperature higher than expected during the thermostat test.

381 A/C clutch cycling too often.

411 RPM out of control during self test low RPM check.

412 RPM out of control during self test high RPM check.

415 Idle air control (IAC) system at adaptive lower learning limit.

416 Idle air control (IAC) system at upper adaptive learning limit.

452 Vehicle speed sensor input too low.

453 Servo leaking down.

454 Servo leaking up.

455 RPM increase insufficient.

456 RPM decrease insufficient.

457 Speed control command switch circuit not working.

458 Speed control command switch stuck or circuit grounded.

459 Speed control ground circuit open.

511 Computer read only memory (ROM) test failed.

512 Computer keep-alive memory (KAM) test failed.

513 Computer internal voltage failure.

519 Power steering pressure switch open.

521* Power steering pressure switch didn’t change states.

522 Transmission not in park or neutral during self test; PNP switch circuit open.

524 Low speed fuel pump circuit open from battery to computer.

525 Vehicle was in gear or A/C was on during self test.

528* Clutch pedal position switch circuit failure.

529 Data communication link or computer failure.

532 Cluster control assembly circuit failure.

533 Data communication link or electronic instrument cluster circuit failure.

536* Brake on/off circuit failure; not actuated during self test.

538* Operator error — computer didn’t perform dynamic response test or cylinder balance test properly, or cylinder balance failed because throttle moved or cylinder ID sensor failed.

539 A/C or defrost on during self test.

542 Fuel pump circuit open from computer to motor ground; fuel pump secondary circuit failure.

543 Fuel pump circuit open from battery to computer; fuel pump secondary circuit failure.

551 Idle air control (IAC) circuit failure.

552 Air management circuit #1 failure — secondary air injection bypass.

553 Air management circuit #2 failure — secondary air injection diverter.

555 Supercharger bypass solenoid circuit failure.

556 Primary fuel pump circuit failure.

557 Low speed primary fuel pump circuit failure.

558 EGR vacuum regulator circuit failure.

559 Air conditioning on relay circuit failure.

562 Auxiliary electrodrive fan circuit failure.

563 High speed fan circuit failure.

564 Fan control circuit failure.

565 Canister purge circuit failure.

566 3-4 shift solenoid circuit failure.

567 Speed control vent circuit failure.

568 Speed control vacuum circuit failure.

569 Auxiliary canister purge circuit failure.

571 EGRA solenoid circuit failure.

572 EGRV solenoid circuit failure.

578 A/C pressure sensor circuit shorted.

579 A/C pressure change insufficient.

581 Power to fan circuit over current.

582 Fan circuit open.

583 Power to fuel pump over current.

584 VCRM power ground circuit open.

585 A/C clutch circuit over current.

586 A/C clutch circuit open.

587 Variable control relay module communication failure.

617 1-2 shift error.

618 2-3 shift error.

619 3-4 shift error.

621 Shift solenoid circuit #1 failure.

622 Shift solenoid circuit #2 failure.

623 Transmission control switch circuit didn’t change states during self test.

624 Electronic pressure control circuit failure.

625 Electronic pressure control driver open in computer.

626 Coast clutch solenoid circuit failure.

627 Torque converter clutch control solenoid circuit failure.

628 Converter clutch has too much slip or error.

629 Torque converter clutch control solenoid circuit failure.

631 Overdrive cancel indicator light or transmission control indicator lamp circuit failure.

632* Overdrive cancel switch circuit or transmission control switch circuit didn’t change states during self test.

633 4x4 switch closed during self test.

634 Manual lever position switch sensor or transmission range out of range. Code may also set if A/C switch was on during self test.

636 Transmission fluid temperature sensor voltage out of range.

637 Transmission fluid temperature sensor circuit voltage too high or open.

638 Transmission fluid temperature sensor circuit voltage too low or grounded.

639 Turbine/transmission speed sensor input too low.

641 Shift solenoid #3 circuit failure.

643 Torque converter clutch circuit failure.

645 1st gear ratio incorrect.

646 2nd gear ratio incorrect.

647 3rd gear ratio incorrect.

648 4th gear ratio incorrect.

649 Electronic pressure control higher or lower than expected.

651 Electronic pressure control circuit failure.

652 Modulated lockup solenoid circuit failure or torque converter clutch control solenoid circuit failure.

653* Transmission control switch didn’t change states during self test.

654 Manual lever position sensor or transmission range sensor didn’t indicate park during self test.

656 Torque converter clutch continuous slip error.

657 Transmission over temperature condition occurred.

659 High vehicle speed in park detected.

667 Transmission range sensor circuit voltage too low.

668 Transmission range sensor circuit voltage too high.

675 Transmission range sensor circuit voltage out of range

998 Hard fault present — computer in FMEM (alternate strategy) mode.

 

* You may have to perform certain steps during self test or a "you blew it" code may appear. A "you blew it" code could also occur from performing the self test on an engine below operating temperature, or wasn't run at 2000 RPM for two minutes to warm the oxygen sensor.

** Indicates the engine control system goes into FMEM (alternate strategy) when this code sets.