TROUBLE CODE DIAGNOSTICS - 7.4L MPI
SERVICE MANUAL NUMBER 23
Code 34 (2 of 3): Manifold Absolute Pressure (MAP) Sensor Circuit (Scan) -
Low Signal Voltage
TEST DESCRIPTION:
Step 2. This step will determine if there is an adequate vacuum supply to the MAP
sensor. If the vacuum gauge reading is erratic, refer to the “Rough or Unstable Idle” in
“Troubleshooting” section.
Step 3. This step determines if DTC 34 is the result of a hard failure or an intermittent
condition. A DTC will set when MAP signal voltage is too low with engine running.
Step 4. This step simulates a DTC 33. If the ECM recognizes the high signal voltage,
the ECM and wiring are OK.
Step 5. This step checks for the 5 volt reference on CKT 416E.
STEP
ACTION
VALUE
YES
NO
PROCEED TO
Go to
Was the “On-Board Diagnostic” (OBD) System
Check Performed?
OBD
System
Check
1
2
–
Step 2
1. Ignition “OFF.”
2.
3.
4.
Install a vacuum gauge.
14
HG
(45.5
kPa)
in.
Start engine and raise RPM to 1000.
The vacuum reading should be steady.
Is the vacuum reading steady and above
the specified value?
Step 3
Step 4
Step 6
Step 7
3
4
Allow the engine to idle.
Does the scan tool indicate MAP sensor
voltage less than the specified value?
1
Volt
1. Ignition “OFF.”
2.
Disconnect MAP sensor harness connec-
tor.
3.
Connect a jumper wire from harness ter-
minal “B” (CKT 432) to harness terminal “C”
(CKT 416E).
3.
Ignition “ON,” engine “OFF.”
Does the scan tool indicate MAP sensor
voltage greater than the specified value?
4
Volts
Volts
Step 10 Step 5
5
1. Ignition “OFF.”
2.
Connect DVOM from harness terminal
“C” (CKT 416E) to a known good ground.
3.
Ignition “ON,” engine “OFF.”
Does the scan tool indicate MAP sensor
voltage greater than the specified value?
4
Step 9
Step 8
Page 5G-56
90-861326--1 MARCH 1999
| Categories | Mercury MerCruiser Manuals |
|---|---|
| Tags | Mercury MerCruiser 454 CID, Mercury MerCruiser 502 CID |
| Model Year | 1998, 1999, 2000, 2001 |
| Download File |
|
| Document File Type | |
| Copyright | Attribution Non-commercial |
(1 votes, average: 5 out of 5)
Marine readers have rated Mercury MerCruiser GM V8 GM V8 454 CID 7.4L and 502 cid 8.2L Marine Engines Service Manual Number 23 5.0 out of 5.0 based on 1 product reviews. Just need the manual. Wrote review. Can't technically review what I haven't seen yet...