A9 LIGHT VEHICLE DIESEL // FLAGSHIP DIAGNOSTIC
2018 DIESEL PICKUP
3.0L TURBO-DIESEL · 80,000 mi · P0671 · cold start + white smoke
Customer concern
"Hard cold start, especially when it's below 50°F overnight. Lots of white smoke that smells like diesel fuel for the first 30 seconds. Once it warms up, runs fine and gets normal fuel economy."
Pre-checks
BATTERY: 12.6V rest, 9.8V crank — OK (cranks normally) FUEL FILTER: Recently replaced — OK DEF LEVEL: 3/4 full — OK GLOW PLUG INDICATOR: Wait-to-start lamp lit — OK (something energizes) SMOKE CHARACTER: White, raw-diesel smell — FAIL HOT START: Instant when warm — OK
Cold-start-only complaint + white smoke that smells like fuel = unburned fuel. Cylinder 1 doesn't have enough heat. Find which glow plug is dead.
Step 1 · Read the smoke
Cold start, ambient 45°F. Watch the tailpipe. White smoke pours out, smells strongly of raw diesel, and fades after about 30 seconds as the engine warms.
Cold-start observation · exhaust
Cold-start white smoke that smells of raw diesel fuel and clears as the engine warms — what does this signature indicate?
Step 2 · Scan the codes
Pull the DTCs and the glow plug live data. The code points at one cylinder — confirm what it's telling you before you reach for parts.
FixedIntel Scan Tool · DTCs
Live data · glow plug system
The PCM reports an open circuit specifically at cylinder 1's glow plug. What's the next physical test to confirm before condemning the plug?
Step 3 · Probe all six plugs
Bus bar removed, multimeter in hand. Tap each glow plug terminal to read resistance across the element. Good plug < 1–2Ω · OL = open. Probe all six, then call the repair.
FixedIntel DMM · glow plug resistance (Ω)
0 / 6 probedTap each cylinder to measure.
Cylinder 1 reads OL (open) and cylinder 5 reads 3.4Ω (above spec but not open). What's the best repair approach?
Step 4 · Rule out the control circuit
Before condemning the elements, prove power actually reaches them. Check the relay, the voltage at every plug terminal during the glow cycle, and the harness.
Relay · harness
Terminal voltage · glow cycle
Cyl 1 sees voltage but draws no current — element is open.
Power reaches every plug terminal at proper voltage. The relay drops 0.4V (acceptable). Harness is clean. What does this rule in/out?
Step 5 · Root cause
Control circuit is healthy, power arrives, the failure is at the elements. Cylinder 1 is dead, cylinder 5 is close behind. Call the root cause and the right repair.
What is the root cause and the proper repair for this customer's cold-start + white smoke complaint?
Diagnosis Closed.
Cylinder 1 glow plug replaced (cyl 5 with it) — clean cold starts restored, no parts cannon.
0:00
Time elapsed
0/60
Score
0%
Efficiency
A9 · DIESEL
Profile +14 pts
Real-shop equivalent
In a real bay, smoke color + smell + when-it-happens localizes a cold-start diesel complaint in minutes — no guesswork, no replacing all six plugs blind, no chasing the relay or PCM. A tech who reads the signature and confirms with a direct resistance test fixes it right the first time and kills the comeback. Every scenario you train sharpens the cert and the daily diagnostic edge.