Repair Order #003

Check Engine

The next repair order landed on Wabbit’s toolbox.

CUSTOMER STATES: CHECK ENGINE LIGHT IS ON.

That was it.

No description.

No symptoms.

Just the light.

Wabbit found the customer waiting beside the car.

“It’s probably just an O₂ sensor,” the customer said.

Wabbit looked at the still-closed hood.

“Maybe.”

“My friend has a scanner.”

Wabbit nodded.

“It said oxygen sensor.”

“Do you know which code it had?”

The customer paused.

“No.”

“Did it show more than one?”

Another pause.

“I don’t think so.”

Wabbit smiled politely.

“Let’s see what the car has to say.”

He pulled it into the diagnostic bay and connected the scan tool.

The screen lit up.

The progress bar moved slowly across the display.

Engine.

Transmission.

ABS.

Airbag.

Body control.

Instrument cluster.

One module after another reported a problem.

When the scan finished, Wabbit stared at the result.

127 STORED FAULTS.

Wabbit blinked.

Then looked at the scanner again.

He scrolled through the list.

Low-voltage faults.

Communication faults.

Missing-message faults.

Sensors reporting values that made absolutely no sense.

Buried somewhere among them was an oxygen-sensor code.

Technically, the customer had been right.

There was an O₂-sensor fault.

It just happened to be standing in a very large crowd.

Mike walked past the bay and noticed Wabbit staring at the scanner.

“What’ve you got?”

Wabbit turned the screen toward him.

Mike stopped.

“Did you scan the car…”

He looked at the number again.

“…or the entire parking lot?”

“Customer thinks it needs an O₂ sensor.”

Mike glanced at the open hood.

Then at the scanner.

“Maybe.”

Wabbit looked back through the faults.

One failed sensor could set a few codes.

It could affect fuel trim.

It could turn on the check-engine light.

It usually couldn't make half the car forget how to talk to the other half.

A list like this usually meant something else.

Low system voltage.

A bad ground.

Damaged wiring.

A communication problem.

Or one electrical failure creating problems everywhere downstream.

Wabbit returned to the service counter.

“The oxygen-sensor fault is there,” he explained. “But it isn’t the only fault.”

“How many are there?”

Wabbit hesitated.

“One hundred twenty-seven.”

The customer blinked.

“So it needs 127 parts?”

“No.”

Wabbit turned the scan tool around.

“It probably needs an electrical diagnosis. Something may be affecting several systems at once.”

“How much is that?”

Wabbit explained the diagnostic time.

The customer looked back toward the car.

Then at the scanner.

“Can’t you just replace the O₂ sensor?”

“I could.”

“Would that turn the light off?”

“Maybe.”

“Would it fix the problem?”

Wabbit looked at the fault count again.

“That’s a lot of possibilities.”

The customer declined the diagnosis.

The O₂ sensor stayed exactly where it was.

So did the check-engine light and all the other codes.

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Service Record

Technician: Wabbit

Customer Complaint: Check-engine light is on.

Diagnosis: 127 stored faults.

Recommendation: Electrical diagnosis.

Status: Customer declined diagnosis.

Lessons Learned: A fault code identifies where the computer noticed a problem. It does not always identify the part that caused it.

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Next Repair Order

Repair Order #004

No Oil Leaks