Powertrain, generic (extended)

P2898 Cylinder 3 Ion Current Sense Circuit

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P2898 marks a basic circuit failure in the ion current measurement of cylinder 3: the engine computer receives nothing it can evaluate from that spark plug. With ion sensing, the plug doubles as a probe, because a bias voltage across the gap drives a small current through the burning, conductive gas. On Saab's Trionic four-cylinders, cylinder 3 shares its start-up spark with cylinder 2 until synchronisation is reached, and only the combustion signal reveals which of the two really burned. The T7 version groups cylinders 3 and 4 on one detector, whose open line to the engine module Saab reports with its own code P1334. No manufacturer publicly documents P2898 itself; coil 3, its connector and the plug are the first checks.

Likely causes

Ignition coil of cylinder 3 whose ion measuring stage has failed
Loose or corroded connector at coil 3 or broken ion signal wire
Faulty cylinder 3 input in the ion processing module or engine module

Symptoms

  • MIL with ion fault stored for cylinder 3
  • Starting may take longer while cylinder identification is uncertain
  • Engine runs with cautious ignition timing and somewhat less power

Repair estimate

DifficultyMediumDIY possible
Parts and labour€60–600
Time0.3–2 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

spark plug cyl 3ignition coil cyl 3ion sense module

Related codes

P2899P289AP289BP2894P289CP0303

References: law.cornell.edu, saabwisonline.com, saabwisonline.com.