Powertrain, generic (extended)

P289E Cylinder 4 Ion Current Sense Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P289E means the ion signal of cylinder 4 remains below the range the module expects. A ground fault on the line from coil 4, a plug whose insulator conducts the bias voltage away, or a coil that has stopped generating that voltage are the main suspects. In Saab's T7 four-cylinder cassette, cylinders 3 and 4 share one detector that pulses engine module pin 6; Saab notes that a short to ground on such a combustion line produced only misfire codes, while an open line was flagged as P1334. A dedicated low code for cylinder 4 separates this case. Since cylinder 4 is also the start partner of cylinder 1, a dead signal can affect synchronisation. The opposite reading is P289F.

Likely causes

Ion signal line of cylinder 4 shorted to ground
Spark plug insulator of cylinder 4 leaking the bias voltage
Bias voltage generation inside coil 4 failed

Symptoms

  • MIL with low ion signal on cylinder 4
  • Possible start delay or misfire codes
  • Power reduced by safety timing on cylinder 4

Repair estimate

DifficultyMediumDIY possible
Parts and labour€30–500
Time0.3–2 h

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

Parts involved

spark plug cyl 4ignition coil cyl 4ion sense module

Related codes

P289CP289DP289FP289AP2892

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