Playbooks

Beginner · short stepsExpert · spec · code · mm

Pick the situation. Read the left column. Say that at the window.

Twelve owner scenarios. Beginner script + genius measurements. SaferCar patterns — not a pirated TSB book.

WhoAudience: Owners in a named jam — brakes, noise, a light, a quote.Anyone who wants both altitudes on one card.
ClickControl: A playbook card. Then the beginner script.Playbook → steps. TSB desk and counter card live next door.
SayCounter: The left-column sentence. Then ask for the number on the right.Measurement first. Campaign lookup second. Parts last.

Playbooks · CEL · Daily owner

Code → don’t throw parts

Check-engine night

The lamp is a pointer, not a parts catalog. Read the code, read the freeze-frame, then authorize a test. A catalytic converter is an expensive way to ignore an exhaust leak.

The orange engine icon is on. It is after hours. You have a $20 scanner or you can get one in the morning. You do not need a Bluetooth dongle we invented. You need the code and a sentence for tomorrow.

Beginner steps

What you do

0 / 5 beginner steps

01Decide if it is a tow nightFlashing CEL, loss of power, overheat, or a noise that was not there yesterday — park it. A solid lamp with a normal drive is usually a morning scan, not a panic tow. When in doubt, tow.Say: If it is flashing I am not driving it to you. Tell me if I should flatbed.
02Type the code from any cheap scannerP, B, C, or U plus four characters. Write stored, pending, and permanent. Translate on /obd. Do not buy the first Amazon part that matches the code title.Say: I have P0420 stored. I want the freeze-frame and a leak check before anyone prices a converter.
03Ask for freeze-frame, not a guessRPM, mph, load, coolant temp, short- and long-term fuel trims. Those five numbers tell highway vs idle, warm vs cold, lean vs rich.Say: Please print or photo the freeze-frame. I will not authorize a cat from the code title.
04Do not clear it to “see if it comes back”Clearing wipes readiness. Some states will fail inspection for incomplete monitors. Permanent codes stay until the monitor runs clean anyway.Say: Please do not clear codes until I have a photo of the list and we agree on the test.
05Authorize a test, then a partSmoke test, fuel-trim snapshot, O2 waveform, compression — whatever matches the family. Diagnosis is a line. The part is a second yes.Say: I will pay the agreed diagnosis. Call me with the measurement before you order the part.

Do not

Do not throw an O2 sensor, a cat, and a MAF on the same visit “to be sure.”
Do not buy a Bluetooth dongle because a site told you that you need their puck.
Do not ignore a flashing lamp — that is catalyst-killing misfire territory.

Expert notes

What the number means

P0420 / P0430 · catalyst efficiency
The rear O2 looks too much like the front. That can be a dying cat — or an exhaust leak before the sensor, a lazy O2, or a misfire that dumped fuel. Do not throw a converter until they have ruled out leaks and upstream faults.
Fuel trims · %
Short-term (STFT) plus long-term (LTFT). Rough rule: combined positive over about +15% at idle is a lean story (vacuum leak, MAF, fuel). Negative is rich (fuel pressure, leaking injector, O2). Context is load and RPM. One number in the driveway is not a sentence.
Coolant temp in frame · °F
A code set at 90 °F is an open-loop / warmup condition. The same code at 195–220 °F is a hot running fault. If they will not tell you the ECT in the freeze-frame, they have not looked.
P0300–P0308 · cylinder
P0300 is random. P0303 is cylinder 3. Swap a coil to another hole before you buy a set. A coil, a plug, an injector, and a compression problem can set the same digit. The digit is the address, not the part.

Open a live desk

SaferCar buckets this card answers: engine · fuel · electrical · stability · exhaust · not CR

Related patterns

Common failures by symptom. SaferCar pointers — not pirated TSB PDFs.

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